Latent imaging for volume Bragg gratings

ABSTRACT

Initiator/mediator chemistry for latent imaging polymers for volume Bragg gratings is provided. Light mediated chemistry including the use of nitroxides allows a first step imaging to occur, where a light induced pattern is recorded in the material, without the grating being apparent. A second bleaching/developing step completes the curing process and reveals the grating.

RELATED APPLICATION

This application claims the benefit of, and priority to, U.S.Provisional Patent Application Ser. No. 62/845,257, filed May 8, 2019,which is incorporated by reference herein in its entirety.

FIELD

Described herein are recording materials for volume holograms, volumeholographic elements, volume holographic gratings, and the like, as wellas the volume holograms, volume holographic elements, volume holographicgratings produced by writing or recording such recording materials.

BACKGROUND

Polymeric substrates are disclosed in the art of holographic recordingmedia, including for example photosensitive polymer films. See, e.g.,Smothers et al., “Photopolymers for Holography,” SPIE OE/LaserConference, 1212 March, Los Angeles, Calif., 1990. The holographicrecording media described in this article contain a photoimageablesystem containing a liquid monomer material (the photoactive monomer)and a photoinitiator (which promotes the polymerization of the monomerupon exposure to light), where the photoimageable system is in anorganic polymer host matrix that is substantially inert to the exposurelight. During writing (recording) of information into the material (bypassing recording light through an array representing data), the monomerpolymerizes in the exposed regions. Due to the lowering of the monomerconcentration caused by the polymerization, monomer from the dark,unexposed regions of the material diffuses to the exposed regions. See,e.g., Colburn and Haines, “Volume Hologram Formation in PhotopolymerMaterials,” Appl. Opt. 10, 1636-1641, 1971. The polymerization andresulting diffusion create a refractive index change, referred to as Δn,thus forming the hologram (holographic grating) representing the data.

Chain length and degree of polymerization are usually maximized anddriven to completion in photopolymer systems used in conventionalapplications such as coatings, sealants, adhesives, etc., usually byusing high light intensities, multifunctional monomers, highconcentrations of monomers, heat, etc. Similar approaches were used inholographic recording media known in the art by using organicphotopolymer formulations high in monomer concentration. See, forexample, U.S. Pat. Nos. 5,874,187 and 5,759,721, disclosing“one-component” organic photopolymer systems. However, suchone-component systems typically have large Bragg detuning values if theyare not precured with light to some extent.

Improvements in holographic photopolymer media have been made byseparating the formation of a polymeric matrix from the photochemistryused to record holographic information. See, for example, U.S. Pat. Nos.6,103,454 and 6,482,551, disclosing “two-component” organic photopolymersystems. Two-component organic photopolymer systems allow for moreuniform starting conditions (e.g., regarding the recording process),more convenient processing and packaging options, and the ability toobtain higher dynamic range media with less shrinkage or Bragg detuning.

Such two-component systems have various issues that need improvement.For example, the performance of a holographic photopolymer is determinedstrongly by how species diffuse during polymerization. Usually,polymerization and diffusion are occurring simultaneously in arelatively uncontrolled fashion within the exposed areas. This leads toseveral undesirable effects: for example, polymers that are not bound tothe matrix after polymerization initiation or termination reactions arefree to diffuse out of exposed regions of the film into unexposed areas,which “blurs” the resulting fringes, reducing Δn and diffractionefficiency of the final hologram. The buildup of Δn during exposuremeans that subsequent exposures can scatter light from these gratings,leading to the formation of noise gratings. These create haze and a lossof clarity in the final waveguide display. As described herein, for aseries of multiplexed exposures with constant dose/exposure, the firstexposures will consume most of the monomer, leading to an exponentialdecrease in diffraction efficiency with each exposure. A complicated“dose scheduling” procedure is required to balance the diffractionefficiency of all of the holograms.

Generally, the storage capacity of a holographic medium is proportionalto the medium's thickness. Deposition onto a substrate of a pre-formedmatrix material containing the photoimageable system typically requiresuse of a solvent, and the thickness of the material is thereforelimited, e.g., to no more than about 150 μm, to allow enough evaporationof the solvent to attain a stable material and reduce void formation.Thus, the need for solvent removal inhibits the storage capacity of amedium.

In contrast, in volume holography, the media thickness is generallygreater than the fringe spacing, and the Klein-Cook Q parameter isgreater than 1. See Klein and Cook, “Unified approach to ultrasoniclight diffraction,” IEEE Transaction on Sonics and Ultrasonics, SU-14,123-134, 1967. Recording mediums formed by polymerizing matrix materialin situ from a fluid mixture of organic oligomer matrix precursor and aphotoimageable system are also known. Because little or no solvent istypically required for deposition of these matrix materials, greaterthicknesses are possible, e.g., 200 μm and above. However, while usefulresults are obtained by such processes, the possibility exists forreaction between the precursors to the matrix polymer and thephotoactive monomer. Such reaction would reduce the refractive indexcontrast between the matrix and the polymerized photoactive monomer,thereby affecting to an extent the strength of the stored hologram.

SUMMARY

The disclosure provides a resin mixture including a partially orcompletely polymerized or crosslinked polymer matrix; a polymerprecursor including a monomer M; and a group of Formula I: where IN isan initiating moiety optionally linked to, or part of, the matrix, -[M]-is a polymerized monomer, and x is an integer from 0 to 50. In someembodiments, IN is linked to, or part of, the matrix, as in Formula II.In some embodiments, IN includes an alkyl amine or a carboxyl group. Insome embodiments, x is 0, as in Formula III, and where

is an optional link to the matrix.

In some embodiments of a resin mixture described herein, the group ofFormula I, Formula II, or Formula III is selected from the groups ofFormulas 101 to 107, where

is an optional link to the matrix.

In some embodiments of a resin mixture described herein, M is selectedfrom an optionally substituted acrylate, an optionally substitutedmethacrylate, an optionally substituted acrylamide, an optionallysubstituted methacrylamide, an optionally substituted styrene, anoptionally substituted vinyl derivative, and an optionally substitutedallyl derivative.

In some embodiments of a resin mixture described herein, x is at least1, and -[M]- is selected from a polymerized optionally substitutedacrylate, a polymerized optionally substituted methacrylate, apolymerized optionally substituted acrylamide, a polymerized optionallysubstituted methacrylamide, a polymerized optionally substitutedstyrene, a polymerized optionally substituted vinyl derivative, and apolymerized optionally substituted allyl derivative.

In some embodiments of a resin mixture described herein, any one ofFormulas I, II, and 101 to 106 is selected from the groups of Formulas1001 to 1011, where x is at least 1; R¹ is selected from hydrogen,optionally substituted alkyl, optionally substituted heteroalkyl,optionally substituted alkenyl, optionally substituted alkynyl,optionally substituted cycloalkyl, optionally substitutedheterocycloalkyl, optionally substituted aryl, optionally substitutedarylalkyl, optionally substituted heteroaryl, and optionally substitutedheteroarylalkyl; R² is independently a group of one, two, three, or fourindependently selected substituents, or no substituent, each substituentindependently including one or more groups selected from optionallysubstituted alkyl, optionally substituted heteroalkyl, optionallysubstituted alkenyl, optionally substituted alkynyl, optionallysubstituted cycloalkyl, optionally substituted heterocycloalkyl,optionally substituted aryl, optionally substituted arylalkyl,optionally substituted heteroaryl, optionally substitutedheteroarylalkyl, hydroxy, halo, cyano, trifluoromethyl,trifluoromethoxy, nitro, trimethylsilanyl, —OR^(a), —SR^(a),—OC(O)—R^(a), —N(R^(a))₂, —C(O)R^(a), —C(O)OR^(a), —OC(O)OR^(a),—OC(O)N(R^(a))₂, —C(O)N(R^(a))₂, —N(R^(a))C(O)OR^(a),—N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂, N(R^(a))C(NR^(a))N(R^(a))₂,—N(R^(a))S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)OR^(a),—S(O)_(t)R^(a), —S(O)_(t)N(R^(a))₂, —S(O)_(t)N(R^(a))C(O)R^(a),(O)P(OR^(a))₃, (S)P(OR^(a))₃, and —(O)P(OR^(a))₂; R³ is selected fromoptionally substituted alkyl, optionally substituted heteroalkyl,optionally substituted alkenyl, optionally substituted alkynyl,optionally substituted cycloalkyl, optionally substitutedheterocycloalkyl, optionally substituted aryl, optionally substitutedarylalkyl, optionally substituted heteroaryl, optionally substitutedheteroarylalkyl, trifluoromethyl, trifluoromethoxy, nitro,trimethylsilanyl, —OR^(a), —SR^(a), —OC(O)—R^(a), —N(R^(a))₂,—C(O)R^(a), —C(O)OR^(a), —OC(O)OR^(a), —OC(O)N(R^(a))₂, —C(O)N(R^(a))₂,—N(R^(a))C(O)OR^(a), —N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂,N(R^(a))C(NR^(a))N(R^(a))₂, —N(R^(a))S(O)_(t)R^(a), —S(O)_(t)OR^(a),—S(O)_(t)R^(a), —S(O)_(t)N(R^(a))₂, —S(O)_(t)N(R^(a))C(O)R^(a),—O(O)P(OR^(a))₂, and —O(S)P(OR^(a))₂; t is 1 or 2; and R^(a) isindependently selected from hydrogen, optionally substituted alkyl,optionally substituted heteroalkyl, optionally substituted alkenyl,optionally substituted alkynyl, optionally substituted cycloalkyl,optionally substituted heterocycloalkyl, optionally substituted aryl,optionally substituted arylalkyl, optionally substituted heteroaryl, andoptionally substituted heteroarylalkyl.

In some embodiments of a resin mixture described herein, the polymermatrix includes a polyurethane fragment. In some embodiments, thepolyurethane is derived from an isocyanate selected from butylenediisocyanate, hexamethylene diisocyanate (HDI), isophorone diisocyanate(IPDI), 1,8-diisocyanato-4-(isocyanatomethyl)octane,2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylenediisocyanate, isomeric bis(4,4′-isocyanatocyclohexyl)methane and anyisomer thereof, isocyanatomethyl-1,8-octane diisocyanate,1,4-cyclohexylene diisocyanate, isomeric cyclohexanedimethylenediisocyanates, 1,4-phenylene diisocyanate, 2,4-toluene diisocyanate,2,6-toluene diisocyanate, 1,5-naphthylene diisocyanate,2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate,and triphenylmethane 4,4′,4″-triisocyanate.

In some embodiments of a resin mixture described herein, a group of anyof Formulas I, II, 101 to 106, and 1001 to 1011, is heat labile. In someembodiments of a resin mixture described herein, a group of any ofFormulas I, II, 101 to 106, and 1001 to 1011, is chemically reactive.

In some embodiments, the disclosure provides a recording material forwriting a volume Bragg grating, the material including a transparentsupport and any resin mixture described herein. In some embodiments, thematerial has a thickness of between 1 μm and 500 μm.

In some embodiments, the disclosure provides a volume Bragg gratingrecorded on any recording material described herein, where the gratingis characterized by a Q parameter equal to or greater than 10, where

$Q = \frac{2{\pi\lambda}_{0}d}{n_{0}\Lambda^{2}}$where λ₀ is a recording wavelength, d is the thickness of the recordingmaterial, n₀ is a refractive index of the recording material, and Λ is agrating constant. In some embodiments of a polymeric material describedherein including any of Formulas I, II, 101 to 106, and 1001 to 1011,the group of any of Formulas I, II, 101 to 106, and 1001 to 1011, isanisotropically distributed throughout the material. In someembodiments, the portions of material having a high concentration of anyof Formulas I, II, 101 to 106, and 1001 to 1011, form a virtual Bragggrating, where the grating is characterized by a Q parameter equal to orgreater than 10, where

$Q = \frac{2{\pi\lambda}_{0}d}{n_{0}\Lambda^{2}}$and where λ₀ is a recording wavelength, d is the thickness of therecording material, n₀ is a refractive index of the recording material,and Λ is a grating constant. In some embodiments, the disclosureprovides a volume Bragg grating obtained by heating any polymericmaterial described herein.

In some embodiments, the disclosure provides a method of recording avolume Bragg grating on any recording material described herein, thematerial including a resin mixture including a partially or completelypolymerized or crosslinked polymer matrix, a polymer precursor includinga monomer M, an initiator precursor Pr—IN optionally linked to, or partof, the matrix, a nitroxide, and an optional sensitizer; the methodincluding subjecting the material to a source of light to generate inthe resin mixture a group of Formula I, where -[M]- is a polymerizedmonomer, x is an integer from 0 to 50, and the group of Formula I isanisotropically distributed throughout the material. In someembodiments, the portions of material having a high concentration ofFormula I form a virtual Bragg grating, where the grating ischaracterized by a Q parameter equal to or greater than 10, where

$Q = \frac{2{\pi\lambda}_{0}d}{n_{0}\Lambda^{2}}$and where λ₀ is a recording wavelength, d is the thickness of therecording material, n₀ is a refractive index of the recording material,and Λ is a grating constant. In some embodiments, the method furtherincludes heating the material to a temperature between about 50° C. andabout 125° C. In some embodiments, the method further includes ableaching step. In some embodiments, IN is linked to, or part of, thematrix, as in Formula II. In some embodiments, IN includes an alkylamine or a carboxyl group. In some embodiments, x is 0, as in FormulaIII, and where

is an optional link to the matrix. In some embodiments, the group ofFormula I, Formula II, or Formula III is selected from the groups ofFormulas 101 to 107, where

is an optional link to the matrix.

In some embodiments, M is selected from an optionally substitutedacrylate, an optionally substituted methacrylate, an optionallysubstituted acrylamide, an optionally substituted methacrylamide, anoptionally substituted styrene, an optionally substituted vinylderivative, and an optionally substituted allyl derivative. In someembodiments, x is at least 1, and -[M]- is selected from a polymerizedoptionally substituted acrylate, a polymerized optionally substitutedmethacrylate, a polymerized optionally substituted acrylamide, apolymerized optionally substituted methacrylamide, a polymerizedoptionally substituted styrene, a polymerized optionally substitutedvinyl derivative, and a polymerized optionally substituted allylderivative. In some embodiments, any one of Formulas I, II, and 101 to106 is selected from the groups of Formulas 1001 to 1011, where x is atleast 1; R¹ is selected from hydrogen, optionally substituted alkyl,optionally substituted heteroalkyl, optionally substituted alkenyl,optionally substituted alkynyl, optionally substituted cycloalkyl,optionally substituted heterocycloalkyl, optionally substituted aryl,optionally substituted arylalkyl, optionally substituted heteroaryl, andoptionally substituted heteroarylalkyl; R² is independently a group ofone, two, three, or four independently selected substituents, or nosubstituent, each substituent independently including one or more groupsselected from optionally substituted alkyl, optionally substitutedheteroalkyl, optionally substituted alkenyl, optionally substitutedalkynyl, optionally substituted cycloalkyl, optionally substitutedheterocycloalkyl, optionally substituted aryl, optionally substitutedarylalkyl, optionally substituted heteroaryl, optionally substitutedheteroarylalkyl, hydroxy, halo, cyano, trifluoromethyl,trifluoromethoxy, nitro, trimethylsilanyl, —OR^(a), —SR^(a),—OC(O)—R^(a), —N(R^(a))₂, —C(O)R^(a), —C(O)OR^(a), —OC(O)OR^(a),—OC(O)N(R^(a))₂, —C(O)N(R^(a))₂, —N(R^(a))C(O)OR^(a),—N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂, N(R^(a))C(NR^(a))N(R^(a))₂,—N(R^(a))S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)OR^(a),—S(O)_(t)R^(a), —S(O)_(t)N(R^(a))₂, —S(O)_(t)N(R^(a))C(O)R^(a),(O)P(OR^(a))₃, (S)P(OR^(a))₃, and —(O)P(OR^(a))₂; R³ is selected fromoptionally substituted alkyl, optionally substituted heteroalkyl,optionally substituted alkenyl, optionally substituted alkynyl,optionally substituted cycloalkyl, optionally substitutedheterocycloalkyl, optionally substituted aryl, optionally substitutedarylalkyl, optionally substituted heteroaryl, optionally substitutedheteroarylalkyl, trifluoromethyl, trifluoromethoxy, nitro,trimethylsilanyl, —OR^(a), —SR^(a), —OC(O)—R^(a), —N(R^(a))₂,—C(O)R^(a), —C(O)OR^(a), —OC(O)OR^(a), —OC(O)N(R^(a))₂, —C(O)N(R^(a))₂,—N(R^(a))C(O)OR^(a), —N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂,N(R^(a))C(NR^(a))N(R^(a))₂, —N(R^(a))S(O)_(t)R^(a), —S(O)_(t)OR^(a),—S(O)_(t)R^(a), —S(O)_(t)N(R^(a))₂, —S(O)_(t)N(R^(a))C(O)R^(a),—O(O)P(OR^(a))₂, and —O(S)P(OR^(a))₂; t is 1 or 2; and R^(a) isindependently selected from hydrogen, optionally substituted alkyl,optionally substituted heteroalkyl, optionally substituted alkenyl,optionally substituted alkynyl, optionally substituted cycloalkyl,optionally substituted heterocycloalkyl, optionally substituted aryl,optionally substituted arylalkyl, optionally substituted heteroaryl, andoptionally substituted heteroarylalkyl.

In some embodiments, the polymer matrix includes a polyurethanefragment. In some embodiments, the polyurethane is derived from anisocyanate selected from butylene diisocyanate, hexamethylenediisocyanate (HDI), isophorone diisocyanate (IPDI),1,8-diisocyanato-4-(isocyanatomethyl)octane,2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylenediisocyanate, isomeric bis(4,4′-isocyanatocyclohexyl)methane and anyisomer thereof, isocyanatomethyl-1,8-octane diisocyanate,1,4-cyclohexylene diisocyanate, isomeric cyclohexanedimethylenediisocyanates, 1,4-phenylene diisocyanate, 2,4-toluene diisocyanate,2,6-toluene diisocyanate, 1,5-naphthylene diisocyanate,2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate,and triphenylmethane 4,4′,4″-triisocyanate.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofthe present disclosure, will be better understood when read inconjunction with the appended drawings.

FIG. 1 illustrates generic steps for forming a volume Bragg grating(VBG). A raw material can be formed by mixing two different ofprecursors, e.g., a matrix precursor, and a photopolymerizable imagingprecursor. The raw material can be formed into a film by curing orcrosslinking, or partially curing or crosslinking the matrix precursor.Finally, holographic exposure initiates the curing or crosslinking ofthe photopolymerizable precursor which is the main step of theholographic recording process of making a VBG.

FIG. 2 is a schematic illustrating the various steps included in acontrolled radical polymerization for holography applications. Thegeneral goals for such applications is the design of a photopolymermaterial that is sensitive to visible light, produces a large Δnresponse, and controls the reaction/diffusion of the photopolymer suchthat chain transfer and termination reactions are reduced or suppressed.The polymerization reaction that occurs inside traditional photopolymermaterials is known as a free radical polymerization, which has severalcharacteristics: radical species are produced immediately upon exposure,radicals initiate polymerization and propagate by adding monomer tochain ends, radicals also react with matrix by hydrogen abstraction andchain transfer reactions, and radicals can terminate by combining withother radicals or reacting with inhibiting species (e.g., O₂).

FIGS. 3A-3C illustrate generally the concept of using a two-stagephotopolymer recording material for volume Bragg gratings, the materialincluding a polymeric matrix (crosslinked lines), and recording,photopolymerizable monomers (circles). As the material is exposed to alight source (arrows, FIG. 3A), the monomer begins to react andpolymerize. Ideally, polymerization occurs only in the light exposedareas, leading to a drop in monomer concentration. As the monomerpolymerizes, a gradient of monomer concentration is created, resultingin monomer diffusing from high monomer concentration areas, toward lowmonomer concentration areas (FIG. 3B). As monomer diffuses into exposedregions, stress builds up in the surrounding matrix polymer as it swellsand “diffuses” to the dark region (FIG. 3C). If the matrix becomes toostressed and cannot swell to accommodate more monomer, diffusion toexposed areas will stop, even if there is a concentration gradient forunreacted monomer. This typically limits the maximum dynamic range ofthe photopolymer, since the buildup of Δn depends on unreacted monomerdiffusing into bright regions.

FIG. 4 illustrates an example of an optical see-through augmentedreality system using a waveguide display that includes an opticalcombiner according to certain embodiments.

FIG. 5A illustrates an example of a volume Bragg grating. FIG. 5Billustrates the Bragg condition for the volume Bragg grating shown inFIG. 5A.

FIG. 6A illustrates the recording light beams for recording a volumeBragg grating according to certain embodiments. FIG. 6B is an example ofa holography momentum diagram illustrating the wave vectors of recordingbeams and reconstruction beams and the grating vector of the recordedvolume Bragg grating according to certain embodiments.

FIG. 7 illustrates an example of a holographic recording system forrecording holographic optical elements according to certain embodiments.

FIG. 8 illustrates a generic process flow for latent imaging bynitroxide-mediated polymerization, including initiation A), quenchingB), and heat stimulated propagation C).

DETAILED DESCRIPTION

Volume gratings, usually produced by holographic technique and known asvolume holographic gratings (VHG), volume Bragg gratings (VBG), orvolume holograms, are diffractive optical elements based on materialwith periodic phase or absorption modulation throughout the entirevolume of the material. When an incident light satisfies Braggcondition, it is diffracted by the grating. The diffraction occurswithin a range of wavelength and incidence angles. In turn, the gratinghas no effect on the light from the off-Bragg angular and spectralrange. These gratings also have multiplexing ability. Due to theseproperties, VHG/VBG are of great interest for various applications inoptics such as data storage and diffractive optical elements fordisplays, fiber optic communication, spectroscopy, etc.

Achieving of the Bragg regime of a diffraction grating is usuallydetermined by Klein parameter Q:

${Q = \frac{2{\pi\lambda}\; d}{n\;\Lambda^{2}}},$where d is a thickness of the grating, λ is the wavelength of light, Λis the grating period, and n is the refractive index of the recordingmedium. As a rule, Bragg conditions are achieved if Q>>1, typically,Q≥10. Thus, to meet Bragg conditions, thickness of diffraction gratingshould be higher than some value determined by parameters of grating,recording medium and light. Because of this, VBG are also called thickgratings. On the contrary, gratings with Q<1 are considered thin, whichtypically demonstrates many diffraction orders (Raman-Nath diffractionregime).

Definitions

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as is commonly understood by one of skill in theart to which this disclosure belongs. All patents and publicationsreferred to herein are incorporated by reference in their entireties.

When ranges are used herein to describe, for example, physical orchemical properties such as molecular weight or chemical formulae, allcombinations and subcombinations of ranges and specific embodimentstherein are intended to be included. Use of the term “about” whenreferring to a number or a numerical range means that the number ornumerical range referred to is an approximation within experimentalvariability (or within statistical experimental error), and thus thenumber or numerical range may vary. The variation is typically from 0%to 15%, or from 0% to 10%, or from 0% to 5% of the stated number ornumerical range. The term “including” (and related terms such as“comprise” or “comprises” or “having” or “including”) includes thoseembodiments such as, for example, an embodiment of any composition ofmatter, method or process that “consist of” or “consist essentially of”the described features.

As used herein, the term “light source” refers to any source ofelectromagnetic radiation of any wavelength. In some embodiments, alight source can be a laser of a particular wavelength.

As used herein, the term “photoinitiating light source” refers to alight source that activates a photoinitiator, a photoactivepolymerizable material, or both. Photoiniating light sources includerecording light, but are not so limited.

As used herein, the term “spatial light intensity” refers to a lightintensity distribution or patterns of varying light intensity within agiven volume of space.

As used herein, the terms “volume Bragg grating,” “volume holographicgrating,” “holographic grating,” and “hologram,” are interchangeablyused to refer to a recorded interference pattern formed when a signalbeam and a reference beam interfere with each other. In someembodiments, and in cases where digital data is recorded, the signalbeam is encoded with a spatial light modulator.

As used herein, the term “holographic recording” refers to a holographicgrating after it is recorded in the holographic recording medium.

As used herein, the term “holographic recording medium” refers to anarticle that is capable of recording and storing, in three dimensions,one or more holographic gratings. In some embodiments, the term refersto an article that is capable of recording and storing, in threedimensions, one or more holographic gratings as one or more pages aspatterns of varying refractive index imprinted into an article.

As used herein, the term “data page” or “page” refers to theconventional meaning of data page as used with respect to holography.For example, a data page may be a page of data, one or more pictures,etc., to be recorded in a holographic recording medium, such as anarticle described herein.

As used herein, the term “recording light” refers to a light source usedto record into a holographic medium. The spatial light intensity patternof the recording light is what is recorded. Thus, if the recording lightis a simple noncoherent beam of light, then a waveguide may be created,or if it is two interfering laser beams, then interference patterns willbe recorded.

As used herein, the term “recording data” refers to storing holographicrepresentations of one or more pages as patterns of varying refractiveindex.

As used herein, the term “reading data” refers to retrieving data storedas holographic representations.

As used herein, the term “exposure” refers to when a holographicrecording medium was exposed to recording light, e.g., when theholographic grating was recorded in the medium.

As used herein, the terms “time period of exposure” and “exposure time”refer interchangeably to how long the holographic recording medium wasexposed to recording light, e.g., how long the recording light was onduring the recording of a holographic grating in the holographicrecording medium. “Exposure time” can refer to the time required torecord a single hologram or the cumulative time for recording aplurality of holograms in a given volume.

As used herein, the term “schedule” refers to the pattern, plan, scheme,sequence, etc., of the exposures relative to the cumulative exposuretime in recording holographic gratings in a medium. In general, theschedule allows one to predict the time (or light energy) needed foreach single exposure, in a set of plural exposures, to give apredetermined diffraction efficiency.

As used herein, the term “function” when used with the term “schedule”refers to a graphical plot or mathematical expression that defines ordescribes a schedule of exposures versus cumulative exposure time inrecording plural holographic gratings.

As used herein, the term “substantially linear function” when used withthe term “schedule” refers to a graphical plot of the schedule ofexposures versus exposure time that provides a straight line orsubstantially a straight line.

As used herein, the term “support matrix” refers to the material,medium, substance, etc., in which the polymerizable component isdissolved, dispersed, embedded, enclosed, etc. In some embodiments, thesupport matrix is typically a low T_(g) polymer. The polymer may beorganic, inorganic, or a mixture of the two. Without being particularlylimited, the polymer may be a thermoset or thermoplastic.

As used herein, the term “different form” refers to an article of thepresent disclosure being processed to form a product having a differentform such as processing an article comprising a block of material,powder of material, chips of material, etc., into a molded product, asheet, a free flexible film, a stiff card, a flexible card, an extrudedproduct, a film deposited on a substrate, etc.

As used herein, the term “particle material” refers to a material thatis made by grinding, shredding, fragmenting or otherwise subdividing anarticle into smaller components or to a material that is comprised ofsmall components such as a powder.

As used herein, the term “free flexible film” refers to a thin sheet offlexible material that maintains its form without being supported on asubstrate. Examples of free flexible films include, without limitation,various types of plastic wraps used in food storage.

As used herein, the term “stiff article” refers to an article that maycrack or crease when bent. Stiff articles include, without limitation,plastic credit cards, DVDs, transparencies, wrapping paper, shippingboxes, etc.

As used herein, the term “volatile compound” refers to any chemical witha high vapor pressure and/or a boiling point below about 150° C.Examples of volatile compounds include: acetone, methylene chloride,toluene, etc. An article, mixture or component is “volatile compoundfree” if the article, mixture or component does not include a volatilecompound.

As used herein, the term “oligomer” refers to a polymer having a limitednumber of repeating units, for example, but without limitation,approximately 30 repeat units or less, or any large molecule able todiffuse at least about 100 nm in approximately 2 minutes at roomtemperature when dissolved in an article of the present disclosure. Sucholigomers may contain one or more polymerizable groups whereby thepolymerizable groups may be the same or different from other possiblemonomers in the polymerizable component. Furthermore, when more than onepolymerizable group is present on the oligomer, they may be the same ordifferent. Additionally, oligomers may be dendritic. Oligomers areconsidered herein to be photoactive monomers, although they aresometimes referred to as “photoactive oligomer(s)”.

As used herein, the term “photopolymerization” refers to anypolymerization reaction caused by exposure to a photoinitiating lightsource.

As used herein, the term “resistant to further polymerization” refers tothe unpolymerized portion of the polymerizable component having adeliberately controlled and substantially reduced rate of polymerizationwhen not exposed to a photoinitiating light source such that darkreactions are minimized, reduced, diminished, eliminated, etc. Asubstantial reduction in the rate of polymerization of the unpolymerizedportion of the polymerizable component according to the presentdisclosure can be achieved by any suitable composition, compound,molecule, method, mechanism, etc., or any combination thereof, includingusing one or more of the following: (1) a polymerization retarder; (2) apolymerization inhibitor; (3) a chain transfer agent; (4) metastablereactive centers; (5) a light or heat labile phototerminator; (6)photo-acid generators, photo-base generators or photogenerated radicals;(7) polarity or solvation effects; (8) counter ion effects; and (9)changes in monomer reactivity.

As used herein, the term “substantially reduced rate” refers to alowering of the polymerization rate to a rate approaching zero, andideally a rate of zero, within seconds after the photoinitiating lightsource is off or absent. The rate of polymerization should typically bereduced enough to prevent the loss in fidelity of previously recordedholograms.

As used herein, the term “dark reaction” refers to any polymerizationreaction that occurs in absence of a photoinitiating light source. Insome embodiments, and without limitation, dark reactions can depleteunused monomer, can cause loss of dynamic range, can cause noisegratings, can cause stray light gratings, or can cause unpredictabilityin the scheduling used for recording additional holograms.

As used herein, the term “free radical polymerization” refers to anypolymerization reaction that is initiated by any molecule comprising afree radical or radicals.

As used herein, the term “cationic polymerization” refers to anypolymerization reaction that is initiated by any molecule comprising acationic moiety or moieties.

As used herein, the term “anionic polymerization” refers to anypolymerization reaction that is initiated by any molecule comprising ananionic moiety or moieties.

As used herein, the term “photoinitiator” refers to the conventionalmeaning of the term photoinitiator and also refers to sensitizers anddyes. In general, a photoinitiator causes the light initiatedpolymerization of a material, such as a photoactive oligomer or monomer,when the material containing the photoinitiator is exposed to light of awavelength that activates the photoinitiator, e.g., a photoinitiatinglight source. The photoinitiator may refer to a combination ofcomponents, some of which individually are not light sensitive, yet incombination are capable of curing the photoactive oligomer or monomer,examples of which include a dye/amine, a sensitizer/iodonium salt, adye/borate salt, etc.

As used herein, the term “photoinitiator component” refers to a singlephotoinitiator or a combination of two or more photoinitiators. Forexample, two or more photoinitiators may be used in the photoinitiatorcomponent of the present disclosure to allow recording at two or moredifferent wavelengths of light.

As used herein, the term “polymerizable component” refers to one or morephotoactive polymerizable materials, and possibly one or more additionalpolymerizable materials, e.g., monomers and/or oligomers, that arecapable of forming a polymer.

As used herein, the term “polymerizable moiety” refers to a chemicalgroup capable of participating in a polymerization reaction, at anylevel, for example, initiation, propagation, etc. Polymerizable moietiesinclude, but are not limited to, addition polymerizable moieties andcondensation polymerizable moieties. Polymerizable moieties include, butare not limited to, double bonds, triple bonds, and the like.

As used herein, the term “photoactive polymerizable material” refers toa monomer, an oligomer and combinations thereof that polymerize in thepresence of a photoinitiator that has been activated by being exposed toa photoinitiating light source, e.g., recording light. In reference tothe functional group that undergoes curing, the photoactivepolymerizable material comprises at least one such functional group. Itis also understood that there exist photoactive polymerizable materialsthat are also photoinitiators, such as N-methylmaleimide, derivatizedacetophenones, etc., and that in such a case, it is understood that thephotoactive monomer and/or oligomer of the present disclosure may alsobe a photoinitiator.

As used herein, the term “photopolymer” refers to a polymer formed byone or more photoactive polymerizable materials, and possibly one ormore additional monomers and/or oligomers.

As used herein, the term “polymerization retarder” refers to one or morecompositions, compounds, molecules, etc., that are capable of slowing,reducing, etc., the rate of polymerization while the photoinitiatinglight source is off or absent, or inhibiting the polymerization of thepolymerizable component when the photoinitiating light source is off orabsent. A polymerization retarder is typically slow to react with aradical (compared to an inhibitor), thus while the photoinitiating lightsource is on, polymerization continues at a reduced rate because some ofthe radicals are effectively terminated by the retarder. In someembodiments, at high enough concentrations, a polymerization retardercan potentially behave as a polymerization inhibitor. In someembodiments, it is desirable to be within the concentration range thatallows for retardation of polymerization to occur, rather thaninhibition of polymerization.

As used herein, the term “polymerization inhibitor” refers to one ormore compositions, compounds, molecules, etc., that are capable ofinhibiting or substantially inhibiting the polymerization of thepolymerizable component when the photoinitiating light source is on oroff. Polymerization inhibitors typically react very quickly withradicals and effectively stop a polymerization reaction. Inhibitorscause an inhibition time during which little to no photopolymer forms,e.g., only very small chains. Typically, photopolymerization occurs onlyafter nearly 100% of the inhibitor is reacted.

As used herein, the term “chain transfer agent” refers to one or morecompositions, compounds, molecules, etc. that are capable ofinterrupting the growth of a polymeric molecular chain by formation of anew radical that may react as a new nucleus for forming a new polymericmolecular chain. Typically, chain transfer agents cause the formation ofa higher proportion of shorter polymer chains, relative topolymerization reactions that occur in the absence of chain transferagents. In some embodiments, certain chain transfer agents can behave asretarders or inhibitors if they do not efficiently reinitiatepolymerization.

As used herein, the term “metastable reactive centers” refers to one ormore compositions, compounds, molecules, etc., that have the ability tocreate pseudo-living radical polymerizations with certain polymerizablecomponents. It is also understood that infrared light or heat may beused to activate metastable reactive centers towards polymerization.

As used herein, the term “light or heat labile phototerminators” refersto one or more compositions, compounds, components, materials,molecules, etc., capable of undergoing reversible termination reactionsusing a light source and/or heat.

As used herein, the terms “photo-acid generators,” “photo-basegenerators,” and “photogenerated radicals,” refer to one or morecompositions, compounds, molecules, etc., that, when exposed to a lightsource, generate one or more compositions, compounds, molecules, etc.,that are acidic, basic, or a free radical.

As used herein, the term “polarity or solvation effects” refers to aneffect or effects that the solvent or the polarity of the medium has onthe polymerization rate. This effect is most pronounced for ionicpolymerizations where the proximity of the counter ion to the reactivechain end influences the polymerization rate.

As used herein, the term “counter ion effects” refers to the effect thatcounter ion, in ionic polymerizations, has on the kinetic chain length.Good counter ions allow for very long kinetic chain lengths, whereaspoor counter ions tend to collapse with the reactive chain end, thusterminating the kinetic chain (e.g., causing smaller chains to beformed).

As used herein, the term “plasticizer” refers to the conventionalmeaning of the term plasticizer. In general, a plasticizer is a compoundadded to a polymer both to facilitate processing and to increase theflexibility and/or toughness of a product by internal modification(solvation) of a polymer molecule.

As used herein, the term “thermoplastic” refers to the conventionalmeaning of thermoplastic, e.g., a composition, compound, substance,etc., that exhibits the property of a material, such as a high polymer,that softens when exposed to heat and generally returns to its originalcondition when cooled to room temperature. Examples of thermoplasticsinclude, but are not limited to: poly(methyl vinyl ether-alt-maleicanhydride), poly(vinyl acetate), poly(styrene), poly(propylene),poly(ethylene oxide), linear nylons, linear polyesters, linearpolycarbonates, linear polyurethanes, etc.

As used herein, the term “room temperature thermoplastic” refers to athermoplastic that is solid at room temperature, e.g., will not coldflow at room temperature.

As used herein, the term “room temperature” refers to the commonlyaccepted meaning of room temperature.

As used herein, the term “thermoset” refers to the conventional meaningof thermoset, e.g., a composition, compound, substance, etc., that iscrosslinked such that it does not have a melting temperature. Examplesof thermosets are crosslinked poly(urethanes), crosslinkedpoly(acrylates), crosslinked poly(styrene), etc.

Unless otherwise stated, the chemical structures depicted herein areintended to include compounds which differ only in the presence of oneor more isotopically enriched atoms. For example, compounds where one ormore hydrogen atoms is replaced by deuterium or tritium, or where one ormore carbon atoms is replaced by ¹³C- or ¹⁴C-enriched carbons, arewithin the scope of this disclosure.

“Alkyl” refers to a straight or branched hydrocarbon chain radicalconsisting solely of carbon and hydrogen atoms, containing nounsaturation, having from one to ten carbon atoms (e.g., (C₁₋₁₀)alkyl orC₁₋₁₀ alkyl). Whenever it appears herein, a numerical range such as “1to 10” refers to each integer in the given range—e.g., “1 to 10 carbonatoms” means that the alkyl group may consist of 1 carbon atom, 2 carbonatoms, 3 carbon atoms, etc., up to and including 10 carbon atoms,although the definition is also intended to cover the occurrence of theterm “alkyl” where no numerical range is specifically designated.Typical alkyl groups include, but are in no way limited to, methyl,ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl isobutyl,tertiary butyl, pentyl, isopentyl, neopentyl, hexyl, septyl, octyl,nonyl and decyl. The alkyl moiety may be attached to the rest of themolecule by a single bond, such as for example, methyl (Me), ethyl (Et),n-propyl (Pr), 1-methylethyl (isopropyl), n-butyl, n-pentyl,1,1-dimethylethyl (t-butyl) and 3-methylhexyl. Unless stated otherwisespecifically in the specification, an alkyl group is optionallysubstituted by one or more of substituents which are independentlyheteroalkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl,arylalkyl, heteroaryl, heteroarylalkyl, hydroxy, halo, cyano,trifluoromethyl, trifluoromethoxy, nitro, trimethylsilanyl, —OR^(a),—SR^(a), —OC(O)—R^(a), —N(R^(a))₂, —C(O)R^(a), —C(O)OR^(a),—OC(O)N(R^(a))₂, —C(O)N(R^(a))₂, —N(R^(a))C(O)OR^(a),—N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂, N(R^(a))C(NR^(a))N(R^(a))₂,—N(R^(a))S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)OR^(a) (where t is1 or 2), —S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)N(R^(a))₂ (where tis 1 or 2), —S(O)_(t)N(R^(a))C(O)R^(a) (where t is 1 or 2), orPO₃(R^(a))₂ where each R^(a) is independently hydrogen, fluoroalkyl,carbocyclyl, carbocyclylalkyl, aryl, aralkyl, heterocycloalkyl,heterocycloalkylalkyl, heteroaryl or heteroarylalkyl.

“Alkylaryl” refers to an -(alkyl)aryl radical where aryl and alkyl areas disclosed herein and which are optionally substituted by one or moreof the substituents described as suitable substituents for aryl andalkyl respectively.

“Alkylhetaryl” refers to an -(alkyl)hetaryl radical where hetaryl andalkyl are as disclosed herein and which are optionally substituted byone or more of the substituents described as suitable substituents foraryl and alkyl respectively.

“Alkylheterocycloalkyl” refers to an -(alkyl) heterocyclyl radical wherealkyl and heterocycloalkyl are as disclosed herein and which areoptionally substituted by one or more of the substituents described assuitable substituents for heterocycloalkyl and alkyl respectively.

An “alkene” moiety refers to a group consisting of at least two carbonatoms and at least one carbon-carbon double bond, and an “alkyne” moietyrefers to a group consisting of at least two carbon atoms and at leastone carbon-carbon triple bond. The alkyl moiety, whether saturated orunsaturated, may be branched, straight chain, or cyclic.

“Alkenyl” refers to a straight or branched hydrocarbon chain radicalgroup consisting solely of carbon and hydrogen atoms, containing atleast one double bond, and having from two to ten carbon atoms (e.g.,(C₂₋₁₀)alkenyl or C₂₋₁₀ alkenyl). Whenever it appears herein, anumerical range such as “2 to 10” refers to each integer in the givenrange—e.g., “2 to 10 carbon atoms” means that the alkenyl group mayconsist of 2 carbon atoms, 3 carbon atoms, etc., up to and including 10carbon atoms. The alkenyl moiety may be attached to the rest of themolecule by a single bond, such as for example, ethenyl (e.g., vinyl),prop-1-enyl (e.g., allyl), but-1-enyl, pent-1-enyl and penta-1,4-dienyl.Unless stated otherwise specifically in the specification, an alkenylgroup is optionally substituted by one or more substituents which areindependently alkyl, heteroalkyl, alkenyl, alkynyl, cycloalkyl,heterocycloalkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, hydroxy,halo, cyano, trifluoromethyl, trifluoromethoxy, nitro, trimethylsilanyl,—OR^(a), —SR^(a), —OC(O)—R^(a), —N(R^(a))₂, —C(O)R^(a), —C(O)OR^(a),—OC(O)N(R^(a))₂, —C(O)N(R^(a))₂, —N(R^(a))C(O)OR^(a),—N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂, N(R^(a))C(NR^(a))N(R^(a))₂,—N(R^(a))S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)OR^(a) (where t is1 or 2), —S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)N(R^(a))₂ (where tis 1 or 2), —S(O)_(t)N(R^(a))C(O)R^(a) (where t is 1 or 2), orPO₃(R^(a))₂, where each R^(a) is independently hydrogen, alkyl,fluoroalkyl, carbocyclyl, carbocyclylalkyl, aryl, aralkyl,heterocycloalkyl, heterocycloalkylalkyl, heteroaryl or heteroarylalkyl.

“Alkenyl-cycloalkyl” refers to an -(alkenyl)cycloalkyl radical wherealkenyl and cycloalkyl are as disclosed herein and which are optionallysubstituted by one or more of the substituents described as suitablesubstituents for alkenyl and cycloalkyl respectively.

“Alkynyl” refers to a straight or branched hydrocarbon chain radicalgroup consisting solely of carbon and hydrogen atoms, containing atleast one triple bond, having from two to ten carbon atoms (e.g.,(C₂₋₁₀)alkynyl or C₂₋₁₀ alkynyl). Whenever it appears herein, anumerical range such as “2 to 10” refers to each integer in the givenrange—e.g., “2 to 10 carbon atoms” means that the alkynyl group mayconsist of 2 carbon atoms, 3 carbon atoms, etc., up to and including 10carbon atoms. The alkynyl may be attached to the rest of the molecule bya single bond, for example, ethynyl, propynyl, butynyl, pentynyl andhexynyl. Unless stated otherwise specifically in the specification, analkynyl group is optionally substituted by one or more substituentswhich independently are: alkyl, heteroalkyl, alkenyl, alkynyl,cycloalkyl, heterocycloalkyl, aryl, arylalkyl, heteroaryl,heteroarylalkyl, hydroxy, halo, cyano, trifluoromethyl,trifluoromethoxy, nitro, trimethylsilanyl, —OR^(a), —SR^(a),—OC(O)—R^(a), —N(R^(a))₂, —C(O)R^(a), —C(O)OR^(a), —OC(O)N(R^(a))₂,—C(O)N(R^(a))₂, —N(R^(a))C(O)OR^(a), —N(R^(a))C(O)R^(a),—N(R^(a))C(O)N(R^(a))₂, N(R^(a))C(NR^(a))N(R^(a))₂,—N(R^(a))S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)OR^(a) (where t is1 or 2), —S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)N(R^(a))₂ (where tis 1 or 2), —S(O)_(t)N(R^(a))C(O)R^(a) (where t is 1 or 2), orPO₃(R^(a))₂, where each R^(a) is independently hydrogen, alkyl,fluoroalkyl, carbocyclyl, carbocyclylalkyl, aryl, aralkyl,heterocycloalkyl, heterocycloalkylalkyl, heteroaryl or heteroarylalkyl.

“Alkynyl-cycloalkyl” refers to an -(alkynyl)cycloalkyl radical wherealkynyl and cycloalkyl are as disclosed herein and which are optionallysubstituted by one or more of the substituents described as suitablesubstituents for alkynyl and cycloalkyl respectively.

“Carboxaldehyde” refers to a —(C═O)H radical.

“Carboxyl” refers to a —(C═O)OH radical.

“Cyano” refers to a —CN radical.

“Cycloalkyl” refers to a monocyclic or polycyclic radical that containsonly carbon and hydrogen, and may be saturated, or partiallyunsaturated. Cycloalkyl groups include groups having from 3 to 10 ringatoms (e.g. (C₃₋₁₀)cycloalkyl or C₃₋₁₀ cycloalkyl). Whenever it appearsherein, a numerical range such as “3 to 10” refers to each integer inthe given range—e.g., “3 to 10 carbon atoms” means that the cycloalkylgroup may consist of 3 carbon atoms, etc., up to and including 10 carbonatoms. Illustrative examples of cycloalkyl groups include, but are notlimited to the following moieties: cyclopropyl, cyclobutyl, cyclopentyl,cyclopentenyl, cyclohexyl, cyclohexenyl, cycloheptyl, cyclooctyl,cyclononyl, cyclodecyl, norbornyl, and the like. Unless stated otherwisespecifically in the specification, a cycloalkyl group is optionallysubstituted by one or more substituents which independently are: alkyl,heteroalkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl,arylalkyl, heteroaryl, heteroarylalkyl, hydroxy, halo, cyano,trifluoromethyl, trifluoromethoxy, nitro, trimethylsilanyl, —OR^(a),—SR^(a), —OC(O)—R^(a), —N(R^(a))₂, —C(O)R^(a), —C(O)OR^(a),—OC(O)N(R^(a))₂, —C(O)N(R^(a))₂, —N(R^(a))C(O)OR^(a),—N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂, N(R^(a))C(NR^(a))N(R^(a))₂,—N(R^(a))S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)OR^(a) (where t is1 or 2), —S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)N(R^(a))₂ (where tis 1 or 2), —S(O)_(t)N(R^(a))C(O)R^(a) (where t is 1 or 2), orPO₃(R^(a))₂, where each R^(a) is independently hydrogen, alkyl,fluoroalkyl, carbocyclyl, carbocyclylalkyl, aryl, aralkyl,heterocycloalkyl, heterocycloalkylalkyl, heteroaryl or heteroarylalkyl.

“Cycloalkyl-alkenyl” refers to a -(cycloalkyl)alkenyl radical wherecycloalkyl and alkenyl are as disclosed herein and which are optionallysubstituted by one or more of the substituents described as suitablesubstituents for cycloalkyl and alkenyl, respectively.

“Cycloalkyl-heterocycloalkyl” refers to a -(cycloalkyl)heterocycloalkylradical where cycloalkyl and heterocycloalkyl are as disclosed hereinand which are optionally substituted by one or more of the substituentsdescribed as suitable substituents for cycloalkyl and heterocycloalkyl,respectively.

“Cycloalkyl-heteroaryl” refers to a -(cycloalkyl)heteroaryl radicalwhere cycloalkyl and heteroaryl are as disclosed herein and which areoptionally substituted by one or more of the substituents described assuitable substituents for cycloalkyl and heteroaryl, respectively.

The term “alkoxy” refers to the group —O-alkyl, including from 1 to 8carbon atoms of a straight, branched, cyclic configuration andcombinations thereof attached to the parent structure through an oxygen.Examples include, but are not limited to, methoxy, ethoxy, propoxy,isopropoxy, cyclopropyloxy and cyclohexyloxy. “Lower alkoxy” refers toalkoxy groups containing one to six carbons.

The term “substituted alkoxy” refers to alkoxy where the alkylconstituent is substituted (e.g., —O-(substituted alkyl)). Unless statedotherwise specifically in the specification, the alkyl moiety of analkoxy group is optionally substituted by one or more substituents whichindependently are: alkyl, heteroalkyl, alkenyl, alkynyl, cycloalkyl,heterocycloalkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, hydroxy,halo, cyano, trifluoromethyl, trifluoromethoxy, nitro, trimethylsilanyl,—OR^(a), —SR^(a), —OC(O)—R^(a), —N(R^(a))₂, —C(O)R^(a), —C(O)OR^(a),—OC(O)N(R^(a))₂, —C(O)N(R^(a))₂, —N(R^(a))C(O)OR^(a),—N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂, N(R^(a))C(NR^(a))N(R^(a))₂,—N(R^(a))S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)OR^(a) (where t is1 or 2), —S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)N(R^(a))₂ (where tis 1 or 2), —S(O)_(t)N(R^(a))C(O)R^(a) (where t is 1 or 2), orPO₃(R^(a))₂, where each R^(a) is independently hydrogen, alkyl,fluoroalkyl, carbocyclyl, carbocyclylalkyl, aryl, aralkyl,heterocycloalkyl, heterocycloalkylalkyl, heteroaryl or heteroarylalkyl.

The term “alkoxycarbonyl” refers to a group of the formula(alkoxy)(C═O)— attached through the carbonyl carbon where the alkoxygroup has the indicated number of carbon atoms. Thus a(C₁₋₆)alkoxycarbonyl group is an alkoxy group having from 1 to 6 carbonatoms attached through its oxygen to a carbonyl linker. “Loweralkoxycarbonyl” refers to an alkoxycarbonyl group where the alkoxy groupis a lower alkoxy group.

The term “substituted alkoxycarbonyl” refers to the group (substitutedalkyl)-O—C(O)— where the group is attached to the parent structurethrough the carbonyl functionality. Unless stated otherwise specificallyin the specification, the alkyl moiety of an alkoxycarbonyl group isoptionally substituted by one or more substituents which independentlyare: alkyl, heteroalkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl,aryl, arylalkyl, heteroaryl, heteroarylalkyl, hydroxy, halo, cyano,trifluoromethyl, trifluoromethoxy, nitro, trimethylsilanyl, —OR^(a),—SR^(a), —OC(O)—R^(a), —N(R^(a))₂, —C(O)R^(a), —C(O)OR^(a),—OC(O)N(R^(a))₂, —C(O)N(R^(a))₂, —N(R^(a))C(O)OR^(a),—N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂, N(R^(a))C(NR^(a))N(R^(a))₂,—N(R^(a))S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)OR^(a) (where t is1 or 2), —S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)N(R^(a))₂ (where tis 1 or 2), —S(O)_(t)N(R^(a))C(O)R^(a) (where t is 1 or 2), orPO₃(R^(a))₂, where each R^(a) is independently hydrogen, alkyl,fluoroalkyl, carbocyclyl, carbocyclylalkyl, aryl, aralkyl,heterocycloalkyl, heterocycloalkylalkyl, heteroaryl or heteroarylalkyl.

“Acyl” refers to the groups (alkyl)-C(O)—, (aryl)-C(O)—,(heteroaryl)-C(O)—, (heteroalkyl)-C(O)— and (heterocycloalkyl)-C(O)—,where the group is attached to the parent structure through the carbonylfunctionality. If the R radical is heteroaryl or heterocycloalkyl, thehetero ring or chain atoms contribute to the total number of chain orring atoms. Unless stated otherwise specifically in the specification,the alkyl, aryl or heteroaryl moiety of the acyl group is optionallysubstituted by one or more substituents which are independently alkyl,heteroalkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl,arylalkyl, heteroaryl, heteroarylalkyl, hydroxy, halo, cyano,trifluoromethyl, trifluoromethoxy, nitro, trimethylsilanyl, —OR^(a),—SR^(a), —OC(O)—R^(a), —N(R^(a))₂, —C(O)R^(a), —C(O)OR^(a),—OC(O)N(R^(a))₂, —C(O)N(R^(a))₂, —N(R^(a))C(O)OR^(a),—N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂, N(R^(a))C(NR^(a))N(R^(a))₂,—N(R^(a))S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)OR^(a) (where t is1 or 2), —S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)N(R^(a))₂ (where tis 1 or 2), —S(O)_(t)N(R^(a))C(O)R^(b) (where t is 1 or 2), orPO₃(R^(a))₂, where each R^(a) is independently hydrogen, alkyl,fluoroalkyl, carbocyclyl, carbocyclylalkyl, aryl, aralkyl,heterocycloalkyl, heterocycloalkylalkyl, heteroaryl or heteroarylalkyl.

“Acyloxy” refers to a R(C═O)O— radical where R is alkyl, aryl,heteroaryl, heteroalkyl or heterocycloalkyl, which are as describedherein. If the R radical is heteroaryl or heterocycloalkyl, the heteroring or chain atoms contribute to the total number of chain or ringatoms. Unless stated otherwise specifically in the specification, the Rof an acyloxy group is optionally substituted by one or moresubstituents which independently are: alkyl, heteroalkyl, alkenyl,alkynyl, cycloalkyl, heterocycloalkyl, aryl, arylalkyl, heteroaryl,heteroarylalkyl, hydroxy, halo, cyano, trifluoromethyl,trifluoromethoxy, nitro, trimethylsilanyl, —OR^(a), —SR^(a),—OC(O)—R^(a), —N(R^(a))₂, —C(O)R^(a), —C(O)OR^(a), —OC(O)N(R^(a))₂,—C(O)N(R^(a))₂, —N(R^(a))C(O)OR^(a), —N(R^(a))C(O)R^(a),—N(R^(a))C(O)N(R^(a))₂, N(R^(a))C(NR^(a))N(R^(a))₂,—N(R^(a))S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)OR^(a) (where t is1 or 2), —S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)N(R^(a))₂ (where tis 1 or 2), —S(O)_(t)N(R^(a))C(O)R^(a) (where t is 1 or 2), orPO₃(R^(a))₂, where each R^(a) is independently hydrogen, alkyl,fluoroalkyl, carbocyclyl, carbocyclylalkyl, aryl, aralkyl,heterocycloalkyl, heterocycloalkylalkyl, heteroaryl or heteroarylalkyl.

“Amino” or “amine” refers to a —N(R^(a))₂ radical group, where eachR^(a) is independently hydrogen, alkyl, fluoroalkyl, carbocyclyl,carbocyclylalkyl, aryl, aralkyl, heterocycloalkyl,heterocycloalkylalkyl, heteroaryl or heteroarylalkyl, unless statedotherwise specifically in the specification. When a —N(R^(a))₂ group hastwo R^(a) substituents other than hydrogen, they can be combined withthe nitrogen atom to form a 4-, 5-, 6- or 7-membered ring. For example,—N(R^(a))₂ is intended to include, but is not limited to, 1-pyrrolidinyland 4-morpholinyl. Unless stated otherwise specifically in thespecification, an amino group is optionally substituted by one or moresubstituents which independently are: alkyl, heteroalkyl, alkenyl,alkynyl, cycloalkyl, heterocycloalkyl, aryl, arylalkyl, heteroaryl,heteroarylalkyl, hydroxy, halo, cyano, trifluoromethyl,trifluoromethoxy, nitro, trimethylsilanyl, —OR^(a), —SR^(a),—OC(O)—R^(a), —N(R^(a))₂, —C(O)R^(a), —C(O)OR^(a), —OC(O)N(R^(a))₂,—C(O)N(R^(a))₂, —N(R^(a))C(O)OR^(a), —N(R^(a))C(O)R^(a),—N(R^(a))C(O)N(R^(a))₂, N(R^(a))C(NR^(a))N(R^(a))₂,—N(R^(a))S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)OR^(a) (where t is1 or 2), —S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)N(R^(a))₂ (where tis 1 or 2), —S(O)_(t)N(R^(a))C(O)R^(a) (where t is 1 or 2),—S(O)_(t)N(R^(a))C(O)R^(a) (where t is 1 or 2), or PO₃(R^(a))₂, whereeach R^(a) is independently hydrogen, alkyl, fluoroalkyl, carbocyclyl,carbocyclylalkyl, aryl, aralkyl, heterocycloalkyl,heterocycloalkylalkyl, heteroaryl or heteroarylalkyl.

The term “substituted amino” also refers to N-oxides of the groups—NHR^(d), and NR^(d)R^(d) each as described above. N-oxides can beprepared by treatment of the corresponding amino group with, forexample, hydrogen peroxide or m-chloroperoxybenzoic acid.

“Amide” or “amido” refers to a chemical moiety with formula —C(O)N(R)₂or —NHC(O)R, where R is selected from the group consisting of hydrogen,alkyl, cycloalkyl, aryl, heteroaryl (bonded through a ring carbon) andheteroalicyclic (bonded through a ring carbon), each of which moiety mayitself be optionally substituted. The R₂ of —N(R)₂ of the amide mayoptionally be taken together with the nitrogen to which it is attachedto form a 4-, 5-, 6- or 7-membered ring. Unless stated otherwisespecifically in the specification, an amido group is optionallysubstituted independently by one or more of the substituents asdescribed herein for alkyl, cycloalkyl, aryl, heteroaryl, orheterocycloalkyl. An amide may be an amino acid or a peptide moleculeattached to a compound disclosed herein, thereby forming a prodrug. Theprocedures and specific groups to make such amides are known to those ofskill in the art and can readily be found in seminal sources such asGreene and Wuts, Protective Groups in Organic Synthesis, 3^(rd) Ed.,John Wiley & Sons, New York, N.Y., 1999, which is incorporated herein byreference in its entirety.

“Aromatic” or “aryl” or “Ar” refers to an aromatic radical with six toten ring atoms (e.g., C₆-C₁₀ aromatic or C₆-C₁₀ aryl) which has at leastone ring having a conjugated pi electron system which is carbocyclic(e.g., phenyl, fluorenyl, and naphthyl). Bivalent radicals formed fromsubstituted benzene derivatives and having the free valences at ringatoms are named as substituted phenylene radicals. Bivalent radicalsderived from univalent polycyclic hydrocarbon radicals whose names endin “-yl” by removal of one hydrogen atom from the carbon atom with thefree valence are named by adding “-idene” to the name of thecorresponding univalent radical, e.g., a naphthyl group with two pointsof attachment is termed naphthylidene. Whenever it appears herein, anumerical range such as “6 to 10” refers to each integer in the givenrange; e.g., “6 to 10 ring atoms” means that the aryl group may consistof 6 ring atoms, 7 ring atoms, etc., up to and including 10 ring atoms.The term includes monocyclic or fused-ring polycyclic (e.g., rings whichshare adjacent pairs of ring atoms) groups. Unless stated otherwisespecifically in the specification, an aryl moiety is optionallysubstituted by one or more substituents which are independently alkyl,heteroalkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl,arylalkyl, heteroaryl, heteroarylalkyl, hydroxy, halo, cyano,trifluoromethyl, trifluoromethoxy, nitro, trimethylsilanyl, —OR^(a),—SR^(a), —OC(O)—R^(a), —N(R^(a))₂, —C(O)R^(a), —C(O)OR^(a),—OC(O)N(R^(a))₂, —C(O)N(R^(a))₂, —N(R^(a))C(O)OR^(a),—N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂, N(R^(a))C(NR^(a))N(R^(a))₂,—N(R^(a))S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)OR^(a) (where t is1 or 2), —S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)N(R^(a))₂ (where tis 1 or 2), —S(O)_(t)N(R^(a))C(O)R^(a) (where t is 1 or 2), orPO₃(R^(a))₂, where each R^(a) is independently hydrogen, alkyl,fluoroalkyl, carbocyclyl, carbocyclylalkyl, aryl, aralkyl,heterocycloalkyl, heterocycloalkylalkyl, heteroaryl or heteroarylalkyl.It is understood that a substituent R attached to an aromatic ring at anunspecified position, (e.g.:

includes one or more, and up to the maximum number of possiblesubstituents.

The term “aryloxy” refers to the group —O-aryl.

The term “substituted aryloxy” refers to aryloxy where the arylsubstituent is substituted (e.g., —O-(substituted aryl)). Unless statedotherwise specifically in the specification, the aryl moiety of anaryloxy group is optionally substituted by one or more substituentswhich independently are: alkyl, heteroalkyl, alkenyl, alkynyl,cycloalkyl, heterocycloalkyl, aryl, arylalkyl, heteroaryl,heteroarylalkyl, hydroxy, halo, cyano, trifluoromethyl,trifluoromethoxy, nitro, trimethylsilanyl, —OR^(a), —SR^(a),—OC(O)—R^(a), —N(R^(a))₂, —C(O)R^(a), —C(O)OR^(a), —OC(O)N(R^(a))₂,—C(O)N(R^(a))₂, —N(R^(a))C(O)OR^(a), —N(R^(a))C(O)R^(a),—N(R^(a))C(O)N(R^(a))₂, N(R^(a))C(NR^(a))N(R^(a))₂,—N(R^(a))S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)OR^(a) (where t is1 or 2), —S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)N(R^(a))₂ (where tis 1 or 2), —S(O)_(t)N(R^(a))C(O)R^(a) (where t is 1 or 2), orPO₃(R^(a))₂, where each R^(a) is independently hydrogen, alkyl,fluoroalkyl, carbocyclyl, carbocyclylalkyl, aryl, aralkyl,heterocycloalkyl, heterocycloalkylalkyl, heteroaryl or heteroarylalkyl.

“Aralkyl” or “arylalkyl” refers to an (aryl)alkyl-radical where aryl andalkyl are as disclosed herein and which are optionally substituted byone or more of the substituents described as suitable substituents foraryl and alkyl respectively.

“Ester” refers to a chemical radical of formula —COOR, where R isselected from the group consisting of alkyl, cycloalkyl, aryl,heteroaryl (bonded through a ring carbon) and heteroalicyclic (bondedthrough a ring carbon). The procedures and specific groups to makeesters are known to those of skill in the art and can readily be foundin seminal sources such as Greene and Wuts, Protective Groups in OrganicSynthesis, 3^(rd) Ed., John Wiley & Sons, New York, N.Y., 1999, which isincorporated herein by reference in its entirety. Unless statedotherwise specifically in the specification, an ester group isoptionally substituted by one or more substituents which independentlyare: alkyl, heteroalkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl,aryl, arylalkyl, heteroaryl, heteroarylalkyl, hydroxy, halo, cyano,trifluoromethyl, trifluoromethoxy, nitro, trimethylsilanyl, —OR^(a),—SR^(a), —OC(O)—R^(a), —N(R^(a))₂, —C(O)R^(a), —C(O)OR^(a),—OC(O)N(R^(a))₂, —C(O)N(R^(a))₂, —N(R^(a))C(O)OR^(a),—N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂, N(R^(a))C(NR^(a))N(R^(a))₂,—N(R^(a))S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)OR^(a) (where t is1 or 2), —S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)N(R^(a))₂ (where tis 1 or 2), —S(O)_(t)N(R^(a))C(O)R^(a) (where t is 1 or 2), orPO₃(R^(a))₂, where each R^(a) is independently hydrogen, alkyl,fluoroalkyl, carbocyclyl, carbocyclylalkyl, aryl, aralkyl,heterocycloalkyl, heterocycloalkylalkyl, heteroaryl or heteroarylalkyl.

“Fluoroalkyl” refers to an alkyl radical, as defined above, that issubstituted by one or more fluoro radicals, as defined above, forexample, trifluoromethyl, difluoromethyl, 2,2,2-trifluoroethyl,1-fluoromethyl-2-fluoroethyl, and the like. The alkyl part of thefluoroalkyl radical may be optionally substituted as defined above foran alkyl group.

“Halo,” “halide,” or, alternatively, “halogen” is intended to meanfluoro, chloro, bromo or iodo. The terms “haloalkyl,” “haloalkenyl,”“haloalkynyl,” and “haloalkoxy” include alkyl, alkenyl, alkynyl andalkoxy structures that are substituted with one or more halo groups orwith combinations thereof. For example, the terms “fluoroalkyl” and“fluoroalkoxy” include haloalkyl and haloalkoxy groups, respectively, inwhich the halo is fluorine.

“Heteroalkyl,” “heteroalkenyl,” and “heteroalkynyl” refer to optionallysubstituted alkyl, alkenyl and alkynyl radicals and which have one ormore skeletal chain atoms selected from an atom other than carbon, e.g.,oxygen, nitrogen, sulfur, phosphorus or combinations thereof. Anumerical range may be given—e.g., C₁-C₄ heteroalkyl which refers to thechain length in total, which in this example is 4 atoms long. Aheteroalkyl group may be substituted with one or more substituents whichindependently are: alkyl, heteroalkyl, alkenyl, alkynyl, cycloalkyl,heterocycloalkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, hydroxy,halo, cyano, nitro, oxo, thioxo, trimethylsilanyl, —OR^(a), —SR^(a),—OC(O)—R^(a), —N(R^(a))₂, —C(O)R^(a), —C(O)OR^(a), —OC(O)N(R^(a))₂,—C(O)N(R^(a))₂, —N(R^(a))C(O)OR^(a), —N(R^(a))C(O)R^(a),—N(R^(a))C(O)N(R^(a))₂, N(R^(a))C(NR^(a))N(R^(a))₂,—N(R^(a))S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)OR^(a) (where t is1 or 2), —S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)N(R^(a))₂ (where tis 1 or 2), —S(O)_(t)N(R^(a))C(O)R^(a) (where t is 1 or 2), orPO₃(R^(a))₂, where each R^(a) is independently hydrogen, alkyl,fluoroalkyl, carbocyclyl, carbocyclylalkyl, aryl, aralkyl,heterocycloalkyl, heterocycloalkylalkyl, heteroaryl or heteroarylalkyl.

“Heteroalkylaryl” refers to an -(heteroalkyl)aryl radical whereheteroalkyl and aryl are as disclosed herein and which are optionallysubstituted by one or more of the substituents described as suitablesubstituents for heteroalkyl and aryl, respectively.

“Heteroalkylheteroaryl” refers to an -(heteroalkyl)heteroaryl radicalwhere heteroalkyl and heteroaryl are as disclosed herein and which areoptionally substituted by one or more of the substituents described assuitable substituents for heteroalkyl and heteroaryl, respectively.

“Heteroalkylheterocycloalkyl” refers to an-(heteroalkyl)heterocycloalkyl radical where heteroalkyl andheterocycloalkyl are as disclosed herein and which are optionallysubstituted by one or more of the substituents described as suitablesubstituents for heteroalkyl and heterocycloalkyl, respectively.

“Heteroalkylcycloalkyl” refers to an -(heteroalkyl)cycloalkyl radicalwhere heteroalkyl and cycloalkyl are as disclosed herein and which areoptionally substituted by one or more of the substituents described assuitable substituents for heteroalkyl and cycloalkyl, respectively.

“Heteroaryl” or “heteroaromatic” or “HetAr” refers to a 5- to18-membered aromatic radical (e.g., C₅-C₁₃ heteroaryl) that includes oneor more ring heteroatoms selected from nitrogen, oxygen and sulfur, andwhich may be a monocyclic, bicyclic, tricyclic or tetracyclic ringsystem. Whenever it appears herein, a numerical range such as “5 to 18”refers to each integer in the given range—e.g., “5 to 18 ring atoms”means that the heteroaryl group may consist of 5 ring atoms, 6 ringatoms, etc., up to and including 18 ring atoms. Bivalent radicalsderived from univalent heteroaryl radicals whose names end in “-yl” byremoval of one hydrogen atom from the atom with the free valence arenamed by adding “-idene” to the name of the corresponding univalentradical—e.g., a pyridyl group with two points of attachment is apyridylidene. A N-containing “heteroaromatic” or “heteroaryl” moietyrefers to an aromatic group in which at least one of the skeletal atomsof the ring is a nitrogen atom. The polycyclic heteroaryl group may befused or non-fused. The heteroatom(s) in the heteroaryl radical areoptionally oxidized. One or more nitrogen atoms, if present, areoptionally quaternized. The heteroaryl may be attached to the rest ofthe molecule through any atom of the ring(s). Examples of heteroarylsinclude, but are not limited to, azepinyl, acridinyl, benzimidazolyl,benzindolyl, 1,3-benzodioxolyl, benzofuranyl, benzooxazolyl,benzo[d]thiazolyl, benzothiadiazolyl, benzo[b][1,4]dioxepinyl,benzo[b][1,4]oxazinyl, 1,4-benzodioxanyl, benzonaphthofuranyl,benzoxazolyl, benzodioxolyl, benzodioxinyl, benzoxazolyl, benzopyranyl,benzopyranonyl, benzofuranyl, benzofuranonyl, benzofurazanyl,benzothiazolyl, benzothienyl(benzothiophenyl),benzothieno[3,2-d]pyrimidinyl, benzotriazolyl,benzo[4,6]imidazo[1,2-a]pyridinyl, carbazolyl, cinnolinyl,cyclopenta[d]pyrimidinyl,6,7-dihydro-5H-cyclopenta[4,5]thieno[2,3-d]pyrimidinyl,5,6-dihydrobenzo[h]quinazolinyl, 5,6-dihydrobenzo[h]cinnolinyl,6,7-dihydro-5H-benzo[6,7]cyclohepta[1,2-c]pyridazinyl, dibenzofuranyl,dibenzothiophenyl, furanyl, furazanyl, furanonyl, furo[3,2-c]pyridinyl,5,6,7,8,9,10-hexahydrocycloocta[d]pyrimidinyl,5,6,7,8,9,10-hexahydrocycloocta[d]pyridazinyl,5,6,7,8,9,10-hexahydrocycloocta[d]pyridinyl, isothiazolyl, imidazolyl,indazolyl, indolyl, indazolyl, isoindolyl, indolinyl, isoindolinyl,isoquinolyl, indolizinyl, isoxazolyl,5,8-methano-5,6,7,8-tetrahydroquinazolinyl, naphthyridinyl,1,6-naphthyridinonyl, oxadiazolyl, 2-oxoazepinyl, oxazolyl, oxiranyl,5,6,6a,7,8,9,10,10a-octahydrobenzo[h]quinazolinyl, 1-phenyl-1H-pyrrolyl,phenazinyl, phenothiazinyl, phenoxazinyl, phthalazinyl, pteridinyl,purinyl, pyranyl, pyrrolyl, pyrazolyl, pyrazolo[3,4-d]pyrimidinyl,pyridinyl, pyrido[3,2-d]pyrimidinyl, pyrido[3,4-d]pyrimidinyl,pyrazinyl, pyrimidinyl, pyridazinyl, pyrrolyl, quinazolinyl,quinoxalinyl, quinolinyl, isoquinolinyl, tetrahydroquinolinyl,5,6,7,8-tetrahydroquinazolinyl,5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidinyl,6,7,8,9-tetrahydro-5H-cyclohepta[4,5]thieno[2,3-d]pyrimidinyl,5,6,7,8-tetrahydropyrido[4,5-c]pyridazinyl, thiazolyl, thiadiazolyl,thiapyranyl, triazolyl, tetrazolyl, triazinyl, thieno[2,3-d]pyrimidinyl,thieno[3,2-d]pyrimidinyl, thieno[2,3-c]pyridinyl, and thiophenyl (e.g.,thienyl). Unless stated otherwise specifically in the specification, aheteroaryl moiety is optionally substituted by one or more substituentswhich are independently: alkyl, heteroalkyl, alkenyl, alkynyl,cycloalkyl, heterocycloalkyl, aryl, arylalkyl, heteroaryl,heteroarylalkyl, hydroxy, halo, cyano, nitro, oxo, thioxo,trimethylsilanyl, —OR^(a), —SR^(a), —OC(O)—R^(a), —N(R^(a))₂,—C(O)R^(a), —C(O)OR^(a), —OC(O)N(R^(a))₂, —C(O)N(R^(a))₂,—N(R^(a))C(O)OR^(a), —N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂,N(R^(a))C(NR^(a))N(R^(a))₂, —N(R^(a))S(O)_(t)R^(a) (where t is 1 or 2),—S(O)_(t)OR^(a) (where t is 1 or 2), —S(O)_(t)R^(a) (where t is 1 or 2),—S(O)_(t)N(R^(a))₂ (where t is 1 or 2), —S(O)_(t)N(R^(a))C(O)R^(a)(where t is 1 or 2), or PO₃(R^(a))₂, where each R^(a) is independentlyhydrogen, alkyl, fluoroalkyl, carbocyclyl, carbocyclylalkyl, aryl,aralkyl, heterocycloalkyl, heterocycloalkylalkyl, heteroaryl orheteroarylalkyl.

Substituted heteroaryl also includes ring systems substituted with oneor more oxide (—O—) substituents, such as, for example, pyridinylN-oxides.

“Heteroarylalkyl” refers to a moiety having an aryl moiety, as describedherein, connected to an alkylene moiety, as described herein, where theconnection to the remainder of the molecule is through the alkylenegroup.

“Heterocycloalkyl” refers to a stable 3- to 18-membered non-aromaticring radical that comprises two to twelve carbon atoms and from one tosix heteroatoms selected from nitrogen, oxygen and sulfur. Whenever itappears herein, a numerical range such as “3 to 18” refers to eachinteger in the given range—e.g., “3 to 18 ring atoms” means that theheterocycloalkyl group may consist of 3 ring atoms, 4 ring atoms, etc.,up to and including 18 ring atoms. Unless stated otherwise specificallyin the specification, the heterocycloalkyl radical is a monocyclic,bicyclic, tricyclic or tetracyclic ring system, which may include fusedor bridged ring systems. The heteroatoms in the heterocycloalkyl radicalmay be optionally oxidized. One or more nitrogen atoms, if present, areoptionally quaternized. The heterocycloalkyl radical is partially orfully saturated. The heterocycloalkyl may be attached to the rest of themolecule through any atom of the ring(s). Examples of suchheterocycloalkyl radicals include, but are not limited to, dioxolanyl,thienyl[1,3]dithianyl, decahydroisoquinolyl, imidazolinyl,imidazolidinyl, isothiazolidinyl, isoxazolidinyl, morpholinyl,octahydroindolyl, octahydroisoindolyl, 2-oxopiperazinyl,2-oxopiperidinyl, 2-oxopyrrolidinyl, oxazolidinyl, piperidinyl,piperazinyl, 4-piperidonyl, pyrrolidinyl, pyrazolidinyl, quinuclidinyl,thiazolidinyl, tetrahydrofuryl, trithianyl, tetrahydropyranyl,thiomorpholinyl, thiamorpholinyl, 1-oxo-thiomorpholinyl, and1,1-dioxo-thiomorpholinyl. Unless stated otherwise specifically in thespecification, a heterocycloalkyl moiety is optionally substituted byone or more substituents which independently are: alkyl, heteroalkyl,alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, arylalkyl,heteroaryl, heteroarylalkyl, hydroxy, halo, cyano, nitro, oxo, thioxo,trimethylsilanyl, —OR^(a), —SR^(a), —OC(O)—R^(a), —N(R^(a))₂,—C(O)R^(a), —C(O)OR^(a), —OC(O)N(R^(a))₂, —C(O)N(R^(a))₂,—N(R^(a))C(O)OR^(a), —N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂,N(R^(a))C(NR^(a))N(R^(a))₂, —N(R^(a))S(O)_(t)R^(a) (where t is 1 or 2),—S(O)_(t)OR^(a) (where t is 1 or 2), —S(O)_(t)R^(a) (where t is 1 or 2),—S(O)_(t)N(R^(a))₂ (where t is 1 or 2), —S(O)_(t)N(R^(a))C(O)R^(a)(where t is 1 or 2), or PO₃(R^(a))₂, where each R^(a) is independentlyhydrogen, alkyl, fluoroalkyl, carbocyclyl, carbocyclylalkyl, aryl,aralkyl, heterocycloalkyl, heterocycloalkylalkyl, heteroaryl orheteroarylalkyl.

“Heterocycloalkyl” also includes bicyclic ring systems where onenon-aromatic ring, usually with 3 to 7 ring atoms, contains at least 2carbon atoms in addition to 1-3 heteroatoms independently selected fromoxygen, sulfur, and nitrogen, as well as combinations including at leastone of the foregoing heteroatoms; and the other ring, usually with 3 to7 ring atoms, optionally contains 1-3 heteroatoms independently selectedfrom oxygen, sulfur, and nitrogen and is not aromatic.

“Nitro” refers to the —NO₂ radical.

“Oxa” refers to the —O— radical.

“Oxo” refers to the ═O radical.

“Isomers” are different compounds that have the same molecular formula.“Stereoisomers” are isomers that differ only in the way the atoms arearranged in space—e.g., having a different stereochemical configuration.“Enantiomers” are a pair of stereoisomers that are non-superimposablemirror images of each other. A 1:1 mixture of a pair of enantiomers is a“racemic” mixture. The term “(±)” is used to designate a racemic mixturewhere appropriate. “Diastereoisomers” are stereoisomers that have atleast two asymmetric atoms, but which are not mirror-images of eachother. The absolute stereochemistry is specified according to theCahn-Ingold-Prelog R-S system. When a compound is a pure enantiomer thestereochemistry at each chiral carbon can be specified by either (R) or(S). Resolved compounds whose absolute configuration is unknown can bedesignated (+) or (−) depending on the direction (dextro- orlevorotatory) which they rotate plane polarized light at the wavelengthof the sodium D line. Certain of the compounds described herein containone or more asymmetric centers and can thus give rise to enantiomers,diastereomers, and other stereoisomeric forms that can be defined, interms of absolute stereochemistry, as (R) or (S). The present chemicalentities, compositions and methods are meant to include all suchpossible isomers, including racemic mixtures, optically pure forms andintermediate mixtures. Optically active (R)- and (S)-isomers can beprepared using chiral synthons or chiral reagents, or resolved usingconventional techniques. When the compounds described herein containolefinic double bonds or other centers of geometric asymmetry, andunless specified otherwise, it is intended that the compounds includeboth E and Z geometric isomers.

“Enantiomeric purity” as used herein refers to the relative amounts,expressed as a percentage, of the presence of a specific enantiomerrelative to the other enantiomer. For example, if a compound, which maypotentially have an (R)- or an (S)-isomeric configuration, is present asa racemic mixture, the enantiomeric purity is about 50% with respect toeither the (R)- or (S)-isomer. If that compound has one isomeric formpredominant over the other, for example, 80% (S)-isomer and 20%(R)-isomer, the enantiomeric purity of the compound with respect to the(S)-isomeric form is 80%. The enantiomeric purity of a compound can bedetermined in a number of ways known in the art, including but notlimited to chromatography using a chiral support, polarimetricmeasurement of the rotation of polarized light, nuclear magneticresonance spectroscopy using chiral shift reagents which include but arenot limited to lanthanide containing chiral complexes or Pirkle'sreagents, or derivatization of a compounds using a chiral compound suchas Mosher's acid followed by chromatography or nuclear magneticresonance spectroscopy.

In some embodiments, enantiomerically enriched compositions havedifferent properties than the racemic mixture of that composition.Enantiomers can be isolated from mixtures by methods known to thoseskilled in the art, including chiral high pressure liquid chromatography(HPLC) and the formation and crystallization of chiral salts; orpreferred enantiomers can be prepared by asymmetric syntheses. See, forexample, Jacques, et al., Enantiomers, Racemates and Resolutions, WileyInterscience, New York (1981); E. L. Eliel, Stereochemistry of CarbonCompounds, McGraw-Hill, New York (1962); and E. L. Eliel and S. H.Wilen, Stereochemistry of Organic Compounds, Wiley-Interscience, NewYork (1994).

The terms “enantiomerically enriched” and “non-racemic,” as used herein,refer to compositions in which the percent by weight of one enantiomeris greater than the amount of that one enantiomer in a control mixtureof the racemic composition (e.g., greater than 1:1 by weight). Forexample, an enantiomerically enriched preparation of the (S)-enantiomer,means a preparation of the compound having greater than 50% by weight ofthe (S)-enantiomer relative to the (R)-enantiomer, such as at least 75%by weight, or such as at least 80% by weight. In some embodiments, theenrichment can be significantly greater than 80% by weight, providing a“substantially enantiomerically enriched” or a “substantiallynon-racemic” preparation, which refers to preparations of compositionswhich have at least 85% by weight of one enantiomer relative to otherenantiomer, such as at least 90% by weight, or such as at least 95% byweight. The terms “enantiomerically pure” or “substantiallyenantiomerically pure” refers to a composition that comprises at least98% of a single enantiomer and less than 2% of the opposite enantiomer.

“Moiety” refers to a specific segment or functional group of a molecule.Chemical moieties are often recognized chemical entities embedded in orappended to a molecule.

“Tautomers” are structurally distinct isomers that interconvert bytautomerization. “Tautomerization” is a form of isomerization andincludes prototropic or proton-shift tautomerization, which isconsidered a subset of acid-base chemistry. “Prototropictautomerization” or “proton-shift tautomerization” involves themigration of a proton accompanied by changes in bond order, often theinterchange of a single bond with an adjacent double bond. Wheretautomerization is possible (e.g., in solution), a chemical equilibriumof tautomers can be reached. An example of tautomerization is keto-enoltautomerization. A specific example of keto-enol tautomerization is theinterconversion of pentane-2,4-dione and 4-hydroxypent-3-en-2-onetautomers. Another example of tautomerization is phenol-ketotautomerization. A specific example of phenol-keto tautomerization isthe interconversion of pyridin-4-ol and pyridin-4(1H)-one tautomers.

A “leaving group or atom” is any group or atom that will, under selectedreaction conditions, cleave from the starting material, thus promotingreaction at a specified site. Examples of such groups, unless otherwisespecified, include halogen atoms and mesyloxy, p-nitrobenzensulphonyloxyand tosyloxy groups.

“Protecting group” is intended to mean a group that selectively blocksone or more reactive sites in a multifunctional compound such that achemical reaction can be carried out selectively on another unprotectedreactive site and the group can then be readily removed or deprotectedafter the selective reaction is complete. A variety of protecting groupsare disclosed, for example, in T. H. Greene and P. G. M. Wuts,Protective Groups in Organic Synthesis, Third Edition, John Wiley &Sons, New York (1999).

“Solvate” refers to a compound in physical association with one or moremolecules of a pharmaceutically acceptable solvent.

“Substituted” means that the referenced group may have attached one ormore additional groups, radicals or moieties individually andindependently selected from, for example, acyl, alkyl, alkylaryl,cycloalkyl, aralkyl, aryl, carbohydrate, carbonate, heteroaryl,heterocycloalkyl, hydroxy, alkoxy, aryloxy, mercapto, alkylthio,arylthio, cyano, halo, carbonyl, ester, thiocarbonyl, isocyanato,thiocyanato, isothiocyanato, nitro, oxo, perhaloalkyl, perfluoroalkyl,phosphate, silyl, sulfinyl, sulfonyl, sulfonamidyl, sulfoxyl, sulfonate,urea, and amino, including mono- and di-substituted amino groups, andprotected derivatives thereof. The substituents themselves may besubstituted, for example, a cycloalkyl substituent may itself have ahalide substituent at one or more of its ring carbons. The term“optionally substituted” means optional substitution with the specifiedgroups, radicals or moieties.

“Sulfanyl” refers to groups that include —S-(optionally substitutedalkyl), —S-(optionally substituted aryl), —S-(optionally substitutedheteroaryl) and —S-(optionally substituted heterocycloalkyl).

“Sulfinyl” refers to groups that include —S(O)—H, —S(O)-(optionallysubstituted alkyl), —S(O)-(optionally substituted amino),—S(O)-(optionally substituted aryl), —S(O)-(optionally substitutedheteroaryl) and —S(O)-(optionally substituted heterocycloalkyl).

“Sulfonyl” refers to groups that include —S(O₂)—H, —S(O₂)-(optionallysubstituted alkyl), —S(O₂)-(optionally substituted amino),—S(O₂)-(optionally substituted aryl), —S(O₂)-(optionally substitutedheteroaryl), and —S(O₂)-(optionally substituted heterocycloalkyl).

“Sulfonamidyl” or “sulfonamido” refers to a —S(═O)₂—NRR radical, whereeach R is selected independently from the group consisting of hydrogen,alkyl, cycloalkyl, aryl, heteroaryl (bonded through a ring carbon) andheteroalicyclic (bonded through a ring carbon). The R groups in —NRR ofthe —S(═O)₂—NRR radical may be taken together with the nitrogen to whichit is attached to form a 4-, 5-, 6- or 7-membered ring. A sulfonamidogroup is optionally substituted by one or more of the substituentsdescribed for alkyl, cycloalkyl, aryl, heteroaryl, respectively.

“Sulfoxyl” refers to a —S(═O)₂OH radical.

“Sulfonate” refers to a —S(═O)₂—OR radical, where R is selected from thegroup consisting of alkyl, cycloalkyl, aryl, heteroaryl (bonded througha ring carbon) and heteroalicyclic (bonded through a ring carbon). Asulfonate group is optionally substituted on R by one or more of thesubstituents described for alkyl, cycloalkyl, aryl, heteroaryl,respectively.

Compounds of the present disclosure also include crystalline andamorphous forms of those compounds, including, for example, polymorphs,pseudopolymorphs, solvates, hydrates, unsolvated polymorphs (includinganhydrates), conformational polymorphs, and amorphous forms of thecompounds, as well as mixtures thereof. “Crystalline form” and“polymorph” are intended to include all crystalline and amorphous formsof the compound, including, for example, polymorphs, pseudopolymorphs,solvates, hydrates, unsolvated polymorphs (including anhydrates),conformational polymorphs, and amorphous forms, as well as mixturesthereof, unless a particular crystalline or amorphous form is referredto.

For the avoidance of doubt, it is intended herein that particularfeatures (for example integers, characteristics, values, uses, diseases,formulae, compounds or groups) described in conjunction with aparticular aspect, embodiment or example of the disclosure are to beunderstood as applicable to any other aspect, embodiment or exampledescribed herein unless incompatible therewith. Thus, such features maybe used where appropriate in conjunction with any of the definition,claims or embodiments defined herein. All of the features disclosed inthis specification (including any accompanying claims, abstract anddrawings), and/or all of the steps of any method or process sodisclosed, may be combined in any combination, except combinations whereat least some of the features and/or steps are mutually exclusive. Thepresent disclosure is not restricted to any details of any disclosedembodiments. The present disclosure extends to any novel one, or novelcombination, of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), or to any novel one, orany novel combination, of the steps of any method or process sodisclosed.

Volume Holography

A holographic recording medium described herein can be used in aholographic system. Formation of a hologram, waveguide, or other opticalarticle relies on a refractive index contrast (Δn) between exposed andunexposed regions of a medium. The amount of information capable ofbeing stored in a holographic medium is a function of the product of:the refractive index contrast, Δn, of the photorecording material, andthe thickness, d, of the photorecording material. The refractive indexcontrast, Δn, is conventionally known, and is defined as the amplitudeof the sinusoidal variations in the refractive index of a material inwhich a plane-wave, volume hologram has been written. The refractiveindex varies as:n(x)=n ₀ +Δn cos(K _(x))where n(x) is the spatially varying refractive index, x is the positionvector, K is the grating wave vector, and n₀ is the baseline refractiveindex of the medium. See, e.g., P. Hariharan, Optical Holography:Principles, Techniques and Applications, Cambridge University Press,Cambridge, 1991, at 44, the disclosure of which is hereby incorporatedby reference. The Δn of a material is typically calculated from thediffraction efficiency or efficiencies of a single volume hologram or amultiplexed set of volume holograms recorded in a medium. The Δn isassociated with a medium before writing, but is observed by measurementperformed after recording. Advantageously, the photorecording materialof the present disclosure exhibits a Δn of 3×10⁻³ or higher.

In some embodiments, this contrast is at least partly due tomonomer/oligomer diffusion to exposed regions. See, e.g., Colburn andHaines, “Volume Hologram Formation in Photopolymer Materials,” Appl.Opt. 10, 1636-1641, 1971; Lesnichii et al., “Study of diffusion in bulkpolymer films below glass transition: evidences of dynamicalheterogeneities,” J. Phys.: Conf. Ser. 1062 012020, 2018. High indexcontrast is generally desired because it provides improved signalstrength when reading a hologram, and provides efficient confinement ofan optical wave in a waveguide. In some embodiments, one way to providehigh index contrast in the present disclosure is to use a photoactivemonomer/oligomer having moieties, referred to for example asindex-contrasting moieties, that are substantially absent from thesupport matrix, and that exhibit a refractive index substantiallydifferent from the index exhibited by the bulk of the support matrix. Insome embodiments, high contrast may be obtained by using a supportmatrix that contains primarily aliphatic or saturated alicyclic moietieswith a low concentration of heavy atoms and conjugated double bondsproviding low index, and a photoactive monomer/oligomer made upprimarily of aromatic or similar high-index moieties.

As described herein, a holographic recording medium is formed such thatholographic writing and reading to the medium are possible. Typically,fabrication of the medium involves depositing a combination, blend,mixture, etc., of the support matrix/polymerizablecomponent/photoinitiator component, as well as any composition,compound, molecule, etc., used to control or substantially reduce therate of polymerization in the absence of a photoinitiating light source(e.g., polymerization retarder), between two plates using, for example,a gasket to contain the mixture. The plates are typically glass, but itis also possible to use other materials transparent to the radiationused to write data, e.g., a plastic such as polycarbonate or poly(methylmethacrylate). It is possible to use spacers between the plates tomaintain a desired thickness for the recording medium. In applicationsrequiring optical flatness, the liquid mixture may shrink during cooling(if a thermoplastic) or curing (if a thermoset) and thus distort theoptical flatness of the article. To reduce such effects, it is useful toplace the article between plates in an apparatus containing mounts,e.g., vacuum chucks, capable of being adjusted in response to changes inparallelism and/or spacing. In such an apparatus, it is possible tomonitor the parallelism in real-time by use of conventionalinterferometric methods, and to make any necessary adjustments to theheating/cooling process. In some embodiments, an article or substrate ofthe present disclosure may have an antireflective coating and/or be edgesealed to exclude water and/or oxygen. An antireflective coating may bedeposited on an article or substrate by various processes such aschemical vapor deposition and an article or substrate may be edge sealedusing known methods. In some embodiments, the photorecording material isalso capable of being supported in other ways. More conventional polymerprocessing can also be used, e.g., closed mold formation or sheetextrusion. A stratified medium can also be used, e.g., a mediumcontaining multiple substrates, e.g., glass, with layers ofphotorecording material disposed between the substrates.

In some embodiments, a holographic film described herein is a filmcomposite consisting of one or more substrate films, one or morephotopolymer films and one or more protective films in any desiredarrangement. In some embodiments, materials or material composites ofthe substrate layer are based on polycarbonate (PC), polyethyleneterephthalate (PET), polybutylene terephthalate, polyethylene,polypropylene, cellulose acetate, cellulose hydrate, cellulose nitrate,cycloolefin polymers, polystyrene, polyepoxides, polysulphone, cellulosetriacetate (CTA), polyamide, polymethyl methacrylate, polyvinylchloride, polyvinyl butyral or polydicyclopentadiene or mixturesthereof. In addition, material composites, such as film laminates orcoextrudates, can be used as substrate film. Examples of materialcomposites are duplex and triplex films having a structure according toone of the schemes A/B, A/B/A or A/B/C, such as PC/PET, PET/PC/PET andPC/TPU (TPU=thermoplastic polyurethane). In some embodiments, PC and PETare used as substrate film. Transparent substrate films which areoptically clear, e.g. not hazy, can be used in some embodiments. Thehaze is measurable via the haze value, which is less than 3.5%, or lessthan 1%, or less than 0.3%. The haze value describes the fraction oftransmitted light which is scattered in a forward direction by thesample through which radiation has passed. Thus, it is a measure of theopacity or haze of transparent materials and quantifies materialdefects, particles, inhomogeneities or crystalline phase boundaries inthe material or its surface that interfere with the transparency. Themethod for measuring the haze is described in the standard ASTM D 1003.

In some embodiments, the substrate film has an optical retardation thatis not too high, e.g. a mean optical retardation of less than 1000 nm,or of less than 700 nm, or of less than 300 nm. The automatic andobjective measurement of the optical retardation is effected using animaging polarimeter. The optical retardation is measured inperpendicular incidence. The retardation values stated for the substratefilm are lateral mean values.

In some embodiments, the substrate film, including possible coatings onone or both sides, has a thickness of 5 to 2000 μm, or of 8 to 300 μm,or of 30 to 200, or of 125 to 175 μm, or of 30 to 45 μm.

In some embodiments, the film composite can have one or more coveringlayers on the photopolymer layer in order to protect it from dirt andenvironmental influences. Plastics films or film composite systems, butalso clearcoats can be used for this purpose. In some embodiments,covering layers are film materials analogous to the materials used inthe substrate film, having a thickness of 5 to 200 μm, or of 8 to 125μm, or of 20 to 50 μm. In some embodiments, covering layers having assmooth a surface as possible are preferred. The roughness can bedetermined according to DIN EN ISO 4288. In some embodiments, roughnessis in the region of less than or equal to 2 μm, or less than or equal to0.5 μm. In some embodiments, PE or PET films having a thickness of 20 to60 μm cam be used as laminating films. In some embodiments, apolyethylene film of 40 μm thickness can be used. In some embodiments,further protective layers, for example a backing of the substrate film,may be used.

In some embodiments, an article described herein can exhibitthermoplastic properties, and can heated above its melting temperatureand processed in ways described herein for the combination, blend,mixture, etc., of the support matrix/polymerizablecomponent/photoinitiator component/polymerization retarder.

Examples of other optical articles include beam filters, beam steerersor deflectors, and optical couplers. See, e.g., Solymar and Cooke,“Volume Holography and Volume Gratings,” Academic Press, 315-327, 1981,incorporated herein by reference. A beam filter separates part of anincident laser beam that is traveling along a particular angle from therest of the beam. Specifically, the Bragg selectivity of a thicktransmission hologram is able to selectively diffract light along aparticular angle of incidence, while light along other angles travelsundeflected through the hologram. See, e.g., Ludman et al., “Very thickholographic nonspatial filtering of laser beams,” Optical Engineering,Vol. 36, No. 6, 1700, 1997, incorporated herein by reference. A beamsteerer is a hologram that deflects light incident at the Bragg angle.An optical coupler is typically a combination of beam deflectors thatsteer light from a source to a target. These articles, typicallyreferred to as holographic optical elements, are fabricated by imaging aparticular optical interference pattern within a recording medium, asdiscussed previously with respect to data storage. Media for theseholographic optical elements are capable of being formed by thetechniques discussed herein for recording media or waveguides.

Materials principles discussed herein are applicable not only tohologram formation, but also to formation of optical transmissiondevices such as waveguides. Polymeric optical waveguides are discussedfor example in Booth, “Optical Interconnection Polymers,” in Polymersfor Lightwave and Integrated Optics, Technology and Applications,Hornak, ed., Marcel Dekker, Inc. (1992); U.S. Pat. No. 5,292,620 (Boothet al.), issued Mar. 18, 1994; and U.S. Pat. No. 5,219,710 (Horn etal.), issued Jun. 15, 1993, incorporated herein by reference. In someembodiments, a recording material described herein is irradiated in adesired waveguide pattern to provide refractive index contrast betweenthe waveguide pattern and the surrounding (cladding) material. It ispossible for exposure to be performed, for example, by a focused laserlight or by use of a mask with a non-focused light source. Generally, asingle layer is exposed in this manner to provide the waveguide pattern,and additional layers are added to complete the cladding, therebycompleting the waveguide.

In one embodiment of the present disclosure, using conventional moldingtechniques, it is possible to mold the combination, blend, mixture,etc., of the support matrix/polymerizable component/photoinitiatorcomponent/polymerization retarder thus realizing a variety of shapesprior to formation of the article by cooling to room temperature. Forexample, the combination, blend, mixture, etc., of the supportmatrix/polymerizable component/photoinitiator component/polymerizationretarder can be molded into ridge waveguides, where a plurality ofrefractive index patterns are then written into the molded structures.It is thereby possible to easily form structures such as Bragg gratings.This feature of the present disclosure increases the breadth ofapplications in which such polymeric waveguides would be useful.

Two-Stage Photopolymers

The purpose of a photopolymer is to faithfully record both phase andamplitude of a three-dimensional optical pattern. During the exposureprocess, the optical pattern is recorded as modulations in refractiveindex inside of the photopolymer film. Light is converted to variationsin refractive index by a photopolymerization reaction, which causes highand low-index species to diffuse to bright and dark fringes,respectively.

A two-stage photopolymer refers to a material that is “cured” twice(FIGS. 3A-3C). It typically consists of (at least) three materials: i)the matrix: typically a low refractive index rubbery polymer (like apolyurethane) that is thermally cured (1st stage) to provide mechanicalsupport during the holographic exposure and ensure the refractive indexmodulation is permanently preserved; ii) the writing monomer: typicallya high index acrylate monomer that reacts with a photoinitiator andpolymerizes quickly; and iii) the photoinitiator (PI) system: thecompound or group of compounds that react with light and initiate thepolymerization of the writing monomer. For visible light polymerization,the PI system usually consists of two compounds that work together. The“dye” or “sensitizer” absorbs light and transfers energy or somereactive species to the “coinitiator,” which actually initiates thepolymerization reaction.

The performance of a holographic photopolymer is determined strongly byhow species diffuse during polymerization. Usually, polymerization &diffusion are occurring simultaneously in a relatively uncontrolledfashion within the exposed areas. This leads to several undesirableeffects. Polymers that are not bound to the matrix after initiation ortermination reactions are free to diffuse out of exposed regions of thefilm into unexposed areas. This “blurs” the resulting fringes, reducingΔn and diffraction efficiency of the final hologram. The buildup of Δnduring exposure means that subsequent exposures can scatter light fromthese gratings, leading to the formation of noise gratings. These createhaze and a loss of clarity in the final waveguide display. For a seriesof multiplexed exposures with constant dose/exposure, the firstexposures will consume most of the monomer, leading to an exponentialdecrease in diffraction efficiency with each exposure. A complicated“dose scheduling” procedure is required to balance the diffractionefficiency of all of the holograms.

As shown in FIG. 2 , controlled radical polymerization can be used inholography applications. The general goals for such applications is thedesign of a photopolymer material that is sensitive to visible light,produces a large Δn response, and controls the reaction/diffusion of thephotopolymer such that chain transfer and termination reactions arereduced or suppressed. The polymerization reaction that occurs insidetraditional photopolymer materials is known as a free radicalpolymerization, which has several characteristics: radical species areproduced immediately upon exposure, radicals initiate polymerization andpropagate by adding monomer to chain ends, radicals also react withmatrix by hydrogen abstraction and chain transfer reactions, andradicals can terminate by combining with other radicals or reacting withinhibiting species (e.g., O₂). Controlled radical polymerization thatcan be used include Atom Transfer Radical Polymerization (ATRP),Reversible Addition-Fragmentation Chain Transfer Polymerization (RAFT),and Nitroxide-mediated Polymerization (NMP).

The matrix is a solid polymer formed in situ from a matrix precursor bya curing step (curing indicating a step of inducing reaction of theprecursor to form the polymeric matrix). It is possible for theprecursor to be one or more monomers, one or more oligomers, or amixture of monomer and oligomer. In addition, it is possible for thereto be greater than one type of precursor functional group, either on asingle precursor molecule or in a group of precursor molecules.Precursor functional groups are the group or groups on a precursormolecule that are the reaction sites for polymerization during matrixcure. To promote mixing with the photoactive monomer, in someembodiments the precursor is liquid at some temperature between about−50° C. and about 80° C. In some embodiments, the matrix polymerizationis capable of being performed at room temperature. In some embodiments,the polymerization is capable of being performed in a time period lessthan 300 minutes, for example between about 5 and about 200 minutes. Insome embodiments, the glass transition temperature (T_(g)) of thephotorecording material is low enough to permit sufficient diffusion andchemical reaction of the photoactive monomer during a holographicrecording process. Generally, the T_(g) is not more than 50° C. abovethe temperature at which holographic recording is performed, which, fortypical holographic recording, means a T_(g) between about 80° C. andabout −130° C. (as measured by conventional methods). In someembodiments, the matrix exhibits a three-dimensional network structure,as opposed to a linear structure, to provide the desired modulusdescribed herein.

In some embodiments, use of a matrix precursor, e.g., the one or morecompounds from which the matrix is formed, and a photoactive monomerthat polymerize by independent reactions, substantially prevents bothcross-reaction between the photoactive monomer and the matrix precursorduring the cure, and inhibition of subsequent monomer polymerization.Use of a matrix precursor and photoactive monomer that form compatiblepolymers substantially avoids phase separation, and in situ formationallows fabrication of media with desirable thicknesses. These materialproperties are also useful for forming a variety of optical articles(optical articles being articles that rely on the formation ofrefractive index patterns or modulations in the refractive index tocontrol or modify light that is directed at them). In addition torecording media, such articles include, but are not limited to, opticalwaveguides, beam steerers, and optical filters.

In some embodiments, independent reactions indicate: (a) the reactionsproceed by different types of reaction intermediates, e.g., ionic vs.free radical, (b) neither the intermediate nor the conditions by whichthe matrix is polymerized will induce substantial polymerization of thephotoactive monomer functional groups, e.g., the group or groups on aphotoactive monomer that are the reaction sites for polymerizationduring the pattern (e.g., hologram) writing process (substantialpolymerization indicates polymerization of more than 20% of the monomerfunctional groups), and (c) neither the intermediate nor the conditionsby which the matrix is polymerized will induce a non-polymerizationreaction of the monomer functional groups that either causescross-reaction between monomer functional groups and the matrix orinhibits later polymerization of the monomer functional groups.

In some embodiments, polymers are considered to be compatible if a blendof the polymers is characterized, in 90° light scattering of awavelength used for hologram formation, by a Rayleigh ratio (R₉₀°) lessthan 7×10⁻³ cm⁻¹. The Rayleigh ratio (R_(θ)) is a conventionally knownproperty, and is defined as the energy scattered by a unit volume in thedirection θ, per steradian, when a medium is illuminated with a unitintensity of unpolarized light, as discussed in Kerker, “The Scatteringof Light and Other Electromagnetic Radiation,” Academic Press, SanDiego, 1969, at 38. The light source used for the measurement isgenerally a laser having a wavelength in the visible part of thespectrum. Normally, the wavelength intended for use in writing hologramsis used. The scattering measurements are made upon a photorecordingmaterial that has been flood exposed. The scattered light is collectedat an angle of 90° from the incident light, typically by aphotodetector. It is possible to place a narrowband filter, centered atthe laser wavelength, in front of such a photodetector to blockfluorescent light, although such a step is not required. The Rayleighratio is typically obtained by comparison to the energy scatter of areference material having a known Rayleigh ratio. Polymers consideredmiscible, e.g., according to conventional tests such as exhibition of asingle glass transition temperature, will typically be compatible aswell. But polymers that are compatible will not necessarily be miscible.In situ indicates that the matrix is cured in the presence of thephotoimageable system. A useful photorecording material, e.g., thematrix material plus the photoactive monomer, photoinitiator, and/orother additives, is attained, the material capable of being formed inthicknesses greater than 200 μm, in some embodiments greater than 500μm, and, upon flood exposure, exhibiting light scattering propertiessuch that the Rayleigh ratio, R₉₀, is less than 7×10⁻³ cm⁻¹. In someembodiments, flood exposure is exposure of the entire photorecordingmaterial by incoherent light at wavelengths suitable to inducesubstantially complete polymerization of the photoactive monomerthroughout the material.

Polymer blends considered miscible, e.g., according to conventionaltests such as exhibition of a single glass transition temperature, willalso typically be compatible, e.g., miscibility is a subset ofcompatibility. Standard miscibility guidelines and tables are thereforeuseful in selecting a compatible blend. However, it is possible forpolymer blends that are immiscible to be compatible according to thelight scattering described herein.

A polymer blend is generally considered miscible if the blend exhibits asingle glass transition temperature, T_(g), as measured by conventionalmethods. An immiscible blend will typically exhibit two glass transitiontemperatures corresponding to the T_(g) values of the individualpolymers. T_(g) testing is most commonly performed by differentialscanning calorimetry (DSC), which shows the T_(g) as a step change inthe heat flow (typically the ordinate). The reported T_(g) is typicallythe temperature at which the ordinate reaches the mid-point betweenextrapolated baselines before and after the transition. It is alsopossible to use Dynamic Mechanical Analysis (DMA) to measure T_(g). DMAmeasures the storage modulus of a material, which drops several ordersof magnitude in the glass transition region. It is possible in certaincases for the polymers of a blend to have individual T_(g) values thatare close to each other. In such cases, conventional methods forresolving such overlapping T_(g) should be used, such as discussed inBrinke et al., “The thermal characterization of multi-component systemsby enthalpy relaxation,” Thermochimica Acta., 238, 75, 1994.

Matrix polymer and photopolymer that exhibit miscibility are capable ofbeing selected in several ways. For example, several publishedcompilations of miscible polymers are available, such as Olabisi et al.,“Polymer-Polymer Miscibility,” Academic Press, New York, 1979; Robeson,MMI. Press Symp. Ser., 2, 177, 1982; Utracki, “Polymer Alloys andBlends: Thermodynamics and Rheology,” Hanser Publishers, Munich, 1989;and S. Krause in Polymer Handbook, J. Brandrup and E. H. Immergut, Eds.;3rd Ed., Wiley Interscience, New York, 1989, pp. VI 347-370,incorporated herein by reference. Even if a particular polymer ofinterest is not found in such references, the approach specified allowsdetermination of a compatible photorecording material by employing acontrol sample.

Determination of miscible or compatible blends is further aided byintermolecular interaction considerations that typically drivemiscibility. For example, polystyrene and poly(methylvinylether) aremiscible because of an attractive interaction between the methyl ethergroup and the phenyl ring. It is therefore possible to promotemiscibility, or at least compatibility, of two polymers by using amethyl ether group in one polymer and a phenyl group in the otherpolymer. Immiscible polymers are also capable of being made miscible bythe incorporation of appropriate functional groups that can provideionic interactions. See Zhou and Eisenberg, J. Polym. Sci., Polym. Phys.Ed., 21 (4), 595, 1983; Murali and Eisenberg, J. Polym. Sci., Part B:Polym. Phys., 26 (7), 1385, 1988; and Natansohn et al., Makromol. Chem.,Macromol. Symp., 16, 175, 1988. For example, polyisoprene andpolystyrene are immiscible. However, when polyisoprene is partiallysulfonated (5%), and 4-vinyl pyridine is copolymerized with thepolystyrene, the blend of these two functionalized polymers is miscible.Without wishing to be bound by any particular theory, it is contemplatedthat the ionic interaction between the sulfonated groups and thepyridine group (proton transfer) is the driving force that makes thisblend miscible. Similarly, polystyrene and poly(ethyl acrylate), whichare normally immiscible, have been made miscible by lightly sulfonatingthe polystyrene. See Taylor-Smith and Register, Macromolecules, 26,2802, 1993. Charge-transfer has also been used to make miscible polymersthat are otherwise immiscible. For example it has been demonstratedthat, although poly(methyl acrylate) and poly(methyl methacrylate) areimmiscible, blends in which the former is copolymerized with(N-ethylcarbazol-3-yl)methyl acrylate (electron donor) and the latter iscopolymerized with 2-[(3,5-dinitrobenzoyl)oxy]ethyl methacrylate(electron acceptor) are miscible, provided the right amounts of donorand acceptor are used. See Piton and Natansohn, Macromolecules, 28, 15,1995. Poly(methyl methacrylate) and polystyrene are also capable ofbeing made miscible using the corresponding donor-acceptor co-monomers.See Piton and Natansohn, Macromolecules, 28, 1605, 1995.

A variety of test methods exist for evaluating the miscibility orcompatibility of polymers, as reflected in the recent overview publishedin Hale and Bair, Ch. 4—“Polymer Blends and Block Copolymers,” ThermalCharacterization of Polymeric Materials, 2nd Ed., Academic Press, 1997.For example, in the realm of optical methods, opacity typicallyindicates a two-phase material, whereas clarity generally indicates acompatible system. Other methods for evaluating miscibility includeneutron scattering, infrared spectroscopy (IR), nuclear magneticresonance (NMR), x-ray scattering and diffraction, fluorescence,Brillouin scattering, melt titration, calorimetry, andchemilluminescence. See, generally, Robeson, herein; Krause,Chemtracts-Macromol. Chem., 2, 367, 1991; Vesely in Polymer Blends andAlloys, Folkes and Hope, Eds., Blackie Academic and Professional,Glasgow, pp. 103-125; Coleman et al. Specific Interactions and theMiscibility of Polymer Blends, Technomic Publishing, Lancaster, Pa.,1991; Garton, Infrared Spectroscopy of Polymer Blends Composites andSurfaces, Hanser, New York, 1992; Kelts et al., Macromolecules, 26,2941, 1993; White and Mirau, Macromolecules, 26, 3049, 1993; White andMirau, Macromolecules, 27, 1648, 1994; and Cruz et al., Macromolecules,12, 726, 1979; Landry et al., Macromolecules, 26, 35, 1993.

In some embodiments, compatibility has also been promoted in otherwiseincompatible polymers by incorporating reactive groups into the polymermatrix, where such groups are capable of reacting with the photoactivemonomer during the holographic recording step. Some of the photoactivemonomer will thereby be grafted onto the matrix during recording. Ifthere are enough of these grafts, it is possible to prevent or reducephase separation during recording. However, if the refractive index ofthe grafted moiety and of the monomer are relatively similar, too manygrafts, e.g., more than 30% of monomers grafted to the matrix, will tendto undesirably reduce refractive index contrast.

The optical article of the present disclosure is formed by stepsincluding mixing a matrix precursor and a photoactive monomer, andcuring the mixture to form the matrix in situ. In some embodiments, thereaction by which the matrix precursor is polymerized during the cure isindependent from the reaction by which the photoactive monomer is laterpolymerized during writing of a pattern, e.g., data or waveguide form,and, in addition, the matrix polymer and the polymer resulting frompolymerization of the photoactive monomer, e.g., the photopolymer, arecompatible with each other. The matrix is considered to be formed whenthe photorecording material exhibits an elastic modulus of at leastabout 10⁵ Pa. In some embodiments, the matrix is considered to be formedwhen the photorecording material, e.g., the matrix material plus thephotoactive monomer, photoinitiator, and/or other additives, exhibits anelastic modulus of at least about 10⁵ Pa. In some embodiments, thematrix is considered to be formed when the photorecording material,e.g., the matrix material plus the photoactive monomer, photoinitiator,and/or other additives, exhibits an elastic modulus of about 10⁵ Pa toabout 10⁹ Pa. In some embodiments, the matrix is considered to be formedwhen the photorecording material, e.g., the matrix material plus thephotoactive monomer, photoinitiator, and/or other additives, exhibits anelastic modulus of about 10⁶ Pa to about 10⁸ Pa.

In some embodiments, an optical article described herein contains athree-dimensional crosslinked polymer matrix and one or more photoactivemonomers. At least one photoactive monomer contains one or moremoieties, excluding the monomer functional groups, that aresubstantially absent from the polymer matrix. Substantially absentindicates that it is possible to find a moiety in the photoactivemonomer such that no more than 20% of all such moieties in thephotorecording material are present, e.g., covalently bonded, in thematrix. The resulting independence between the host matrix and themonomer offers useful recording properties in holographic media anddesirable properties in waveguides such as enabling formation of largemodulations in the refractive index without the need for highconcentrations of the photoactive monomer. Moreover, it is possible toform the material without solvent development.

In some embodiments, media that utilize a matrix precursor andphotoactive monomer that polymerize by non-independent reactions can beused, resulting in substantial cross-reaction between the precursor andthe photoactive monomer during the matrix cure (e.g., greater than 20%of the monomer is attached to the matrix after cure), or other reactionsthat inhibit polymerization of the photoactive monomer. Cross-reactiontends to reduce the refractive index contrast between the matrix and thephotoactive monomer and is capable of affecting the subsequentpolymerization of the photoactive monomer, and inhibition of monomerpolymerization clearly affects the process of writing holograms. As forcompatibility, previous work has been concerned with the compatibilityof the photoactive monomer in a matrix polymer, not the compatibility ofthe resulting photopolymer in the matrix. Yet, where the photopolymerand matrix polymer are not compatible, phase separation typically occursduring hologram formation. It is possible for such phase separation tolead to increased light scattering, reflected in haziness or opacity,thereby degrading the quality of the medium, and the fidelity with whichstored data is capable of being recovered.

In one embodiment, the support matrix is thermoplastic and allows anarticle described herein to behave as if the entire article was athermoplastic. That is, the support matrix allows the article to beprocessed similar to the way that a thermoplastic is processed, e.g.,molded into a shaped article, blown into a film, deposited in liquidform on a substrate, extruded, rolled, pressed, made into a sheet ofmaterial, etc. and then allowed to harden at room temperature to take ona stable shape or form. The support matrix may comprise one or morethermoplastics. Suitable thermoplastics include poly(methyl vinylether-alt-maleic anhydride), poly(vinyl acetate), poly(styrene),poly(propylene), poly(ethylene oxide), linear nylons, linear polyesters,linear polycarbonates, linear polyurethanes, poly(vinyl chloride),poly(vinyl alcohol-co-vinyl acetate), and the like. In some embodiments,polymerization reactions that can be used for forming matrix polymersinclude cationic epoxy polymerization, cationic vinyl etherpolymerization, cationic alkenyl ether polymerization, cationic alleneether polymerization, cationic ketene acetal polymerization, epoxy-aminestep polymerization, epoxy-mercaptan step polymerization, unsaturatedester-amine step polymerization (e.g., via Michael addition),unsaturated ester-mercaptan step polymerization (e.g., via Michaeladdition), vinyl-silicon hydride step polymerization (hydrosilylation),isocyanate-hydroxyl step polymerization (e.g., urethane formation),isocyanate-amine step polymerization (e.g., urea formation), and thelike.

In some embodiments, the photopolymer formulations described hereininclude matrix polymers obtainable by reacting a polyisocyanatecomponent with an isocyanate-reactive component. The isocyanatecomponent preferably comprises polyisocyanates. Polyisocyanates that maybe used are all compounds known per se to a person skilled in the art ormixtures thereof, that have on average two or more NCO functions permolecule. These may have an aromatic, araliphatic, aliphatic orcycloaliphatic basis. Monoisocyanates and/or polyisocyanates containingunsaturated groups may also be concomitantly used in minor amounts. Insome embodiments, the isocyanate component includes one or more ofbutylene diisocyanate, hexamethylene diisocyanate (HDI), isophoronediisocyanate (IPDI), 1,8-diisocyanato-4-(isocyanatomethyl)octane, 2,2,4-and/or 2,4,4-trimethylhexamethylene diisocyanate, the isomericbis(4,4′-isocyanatocyclohexyl)methane and mixtures thereof having anydesired isomer content, isocyanatomethyl-1,8-octane diisocyanate,1,4-cyclohexylene diisocyanate, the isomeric cyclohexanedimethylenediisocyanates, 1,4-phenylene diisocyanate, 2,4- and/or 2,6-toluenediisocyanate, 1,5-naphthylene diisocyanate, 2,4′- or4,4′-diphenylmethane diisocyanate and/or triphenylmethane4,4′,4″-triisocyanate are suitable. Use of derivatives of monomeric di-or triisocyanates having urethane, urea, carbodiimide, acylurea,isocyanurate, allophanate, biuret, oxadiazinetrione, uretdione and/oriminooxadiazinedione structures is also possible. In some embodiments,the use of polyisocyanates based on aliphatic and/or cycloaliphatic di-or triisocyanates is preferred. In some embodiments, the polyisocyanatesare di- or oligomerized aliphatic and/or cycloaliphatic di- ortriisocyanates. In some embodiments, isocyanurates, uretdiones and/oriminooxadiazinediones based on HDI and1,8-diisocyanato-4-(isocyanatomethyl)octane or mixtures thereof arepreferred.

In some embodiments, NCO-functional prepolymers having urethane,allophanate, biuret and/or amide groups can be used. Prepolymers canalso be obtained in a manner known per se to the person skilled in theart by reacting monomeric, oligomeric or polyisocyanates withisocyanate-reactive compounds in suitable stoichiometry with optionaluse of catalysts and solvents. In some embodiments, suitablepolyisocyanates are all aliphatic, cycloaliphatic, aromatic oraraliphatic di- and triisocyanates known per se to the person skilled inthe art, it being unimportant whether these were obtained by means ofphosgenation or by phosgene-free processes. In addition, the highermolecular weight subsequent products of monomeric di- and/ortriisocyanates having a urethane, urea, carbodiimide, acylurea,isocyanurate, allophanate, biuret, oxadiazinetrione, uretdione oriminooxadiazinedione structure, which are well known per se to a personskilled in the art, can also be used, in each case individually or inany desired mixtures with one another. Examples of suitable monomericdi- or triisocyanates which can be used are butylene diisocyanate,hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI),trimethylhexamethylene diisocyanate (TMDI),1,8-diisocyanato-4-(isocyanatomethyl)octane, isocyanatomethyl-1,8-octanediisocyanate (TIN), 2,4- and/or 2,6-toluene diisocyanate.

OH-functional compounds are preferably used as isocyanate-reactivecompounds for synthesizing the prepolymers. Said compounds are analogousto other OH-functional compounds described herein. In some embodiments,OH-functional compounds are polyester polyols and/or polyether polyolshaving number average molar masses of 200 to 6200 g/mol. Difunctionalpolyether polyols based on ethylene glycol and propylene glycol, theproportion of propylene glycol accounting for at least 40% by weight,and polymers of tetrahydrofuran having number average molar masses of200 to 4100 g/mol and aliphatic polyester polyols having number averagemolar masses of 200 to 3100 g/mol can be used. Difunctional polyetherpolyols based on ethylene glycol and propylene glycol, the proportion ofpropylene glycol accounting for at least 80% by weight (in particularpure polypropylene glycols), and polymers of tetrahydrofuran havingnumber average molar masses of 200 to 2100 g/mol can be used in someembodiments. Adducts of butyrolactone, ε-caprolactone and/ormethyl-ε-caprolactone (in particular ε-caprolactone) with aliphatic,araliphatic or cycloaliphatic di-, tri- or polyfunctional alcoholscontaining 2 to 20 carbon atoms (in particular difunctional aliphaticalcohols having 3 to 12 carbon atoms) can be used in some embodiments.In some embodiments, these adducts have number average molar masses of200 to 2000 g/mol, or of 500 to 1400 g/mol.

Allophanates may also be used as a mixture with other prepolymers oroligomers. In these cases, the use of OH-functional compounds havingfunctionalities of 1 to 3.1 is advantageous. When monofunctionalalcohols are used, those having 3 to 20 carbon atoms are preferred.

It is also possible to use amines for the prepolymer preparation. Forexample, ethylenediamine, diethylenetriamine, triethylenetetramine,propylenediamine, diaminocyclohexane, diaminobenzene, diaminobisphenyl,difunctional polyamines, for example, the Jeffamines®, amine-terminatedpolymers having number average molar masses of up to 10 000 g/mol or anydesired mixtures thereof with one another are suitable.

For the preparation of prepolymers containing biuret groups, an excessof isocyanate is reacted with amine, a biuret group forming. In thiscase, suitable amines for the reaction with the di-, tri- andpolyisocyanates mentioned are all oligomeric or polymeric, primary orsecondary, difunctional amines described herein. Aliphatic biurets basedon aliphatic amines and aliphatic isocyanates can be used in someembodiments. Low molecular weight biurets having number average molarmasses of less than 2000 g/mol, based on aliphatic diamines ordifunctional polyamines and aliphatic diisocyanates, in particular HDIand TMDI, can be used in some embodiments.

In some embodiments, prepolymers are urethanes, allophanates or biuretsobtained from aliphatic isocyanate-functional compounds and oligomericor polymeric isocyanate-reactive compounds having number average molarmasses of 200 to 10 000 g/mol; urethanes, allophanates or biuretsobtained from aliphatic isocyanate-functional compounds and polyolshaving number average molar masses of 200 to 6200 g/mol or (poly)amineshaving number average molar masses of less than 3000 g/mol can be usedin some embodiments, and allophanates obtained from HDI or TMDI anddifunctional polyether polyols (in particular polypropylene glycols)having number average molar masses of 200 to 2100 g/mol, urethanesobtained from HDI or TMDI, based on adducts of butyrolactone,ε-caprolactone and/or methyl-ε-caprolactone (in particularε-caprolactone) with aliphatic, araliphatic or cycloaliphatic di-, tri-or polyfunctional alcohols containing 2 to 20 carbon atoms (inparticular with difunctional aliphatic alcohols having 3 to 12 carbonatoms), having number average molar masses of 500 to 3000 g/mol,particularly preferably of 1000 to 2000 g/mol (in particular as amixture with other oligomers of difunctional aliphatic isocyanates) orurethanes obtained from HDI or TMDI, based on trifunctional polyetherpolyols (in particular polypropylene glycol) having number average molarmasses between 2000 and 6200 g/mol and biurets obtained from HDI or TMDIwith difunctional amines or polyamines having number average molarmasses of 200 to 1400 g/mol (in particular also as a mixture with otheroligomers of difunctional aliphatic isocyanates) can be used in someembodiments. In some embodiments, the prepolymers described herein haveresidue contents of free monomeric isocyanate of less than 2% by weight,or less than 1.0% by weight, or less than 0.5% by weight.

In some embodiments, the isocyanate component contains proportionatelyfurther isocyanate components in addition to the prepolymers described.Aromatic, araliphatic, aliphatic and cycloaliphatic di-, tri- orpolyisocyanates are suitable for this purpose used. It is also possibleto use mixtures of such di-, tri- or polyisocyanates. Examples ofsuitable di-, tri- or polyisocyanates are butylene diisocyanate,hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI),1,8-diisocyanato-4-(isocyanatomethyl)octane, 2,2,4- and/or2,4,4-trimethylhexamethylene diisocyanate (TMDI), the isomericbis(4,4′-isocyanatocyclohexyl)methanes and mixtures thereof having anydesired isomer content, isocyanatomethyl-1,8-octane diisocyanate,1,4-cyclohexylene diisocyanate, the isomeric cyclohexanedimethylenediisocyanates, 1,4-phenylene diisocyanate, 2,4- and/or 2,6-toluenediisocyanate, 1,5-naphthylene diisocyanate, 2,4′- or4,4′-diphenylmethane diisocyanate, triphenylmethane4,4′,4″-triisocyanate or derivatives thereof having a urethane, urea,carbodiimide, acylurea, isocyanurate, allophanate, biuret,oxadiazinetrione, uretdione, or iminooxadiazinedione structure andmixtures thereof. Polyisocyanates based on oligomerized and/orderivatized diisocyanates which were freed from excess diisocyanate bysuitable processes are preferred, in particular those of hexamethylenediisocyanate. The oligomeric isocyanurates, uretdiones andiminooxadiazinediones of HDI and mixtures thereof can be used in someembodiments.

In some embodiments, it is optionally also possible for the isocyanatecomponent proportionately to contain isocyanates that have been partlyreacted with isocyanate-reactive ethylenically unsaturated compounds.α,β-Unsaturated carboxylic acid derivatives, such as acrylates,methacrylates, maleates, fumarates, maleimides, acrylamides and vinylethers, propenyl ethers, allyl ethers and compounds which containdicyclopentadienyl units and have at least one group reactive towardsisocyanates can be used in some embodiments as isocyanate-reactiveethylenically unsaturated compounds; acrylates and methacrylates havingat least one isocyanate-reactive group can be used in some embodiments.Suitable hydroxy-functional acrylates or methacrylates are, for example,compounds such as 2-hydroxyethyl(meth)acrylate, polyethylene oxidemono(meth)acrylates, polypropylene oxide mono(meth)-acrylates,polyalkylene oxide mono(meth)acrylates,poly(ε-caprolactone)mono(meth)-acrylates, such as, for example, Tone®M100 (Dow, USA), 2-hydroxypropyl(meth)acrylate,4-hydroxybutyl(meth)acrylate,3-hydroxy-2,2-dimethylpropyl(meth)acrylate, the hydroxy-functionalmono-, di- or tetra(meth)acrylates of polyhydric alcohols, such astrimethylolpropane, glycerol, pentaerythritol, dipentaerythritol,ethoxylated, propoxylated or alkoxylated trimethylolpropane, glycerol,pentaerythritol, dipentaerythritol or the industrial mixtures thereof.In addition, isocyanate-reactive oligomeric or polymeric unsaturatedcompounds containing acrylate and/or methacrylate groups, alone or incombination with the abovementioned monomeric compounds, are suitable.The proportion of isocyanates which have been partly reacted withisocyanate-reactive ethylenically unsaturated compounds, based on theisocyanate component, is 0 to 99%, or 0 to 50%, or 0 to 25% or 0 to 15%.

In some embodiments, it is optionally also possible for the isocyanatecomponent to contain, completely or proportionately, isocyanates whichhave been reacted completely or partly with blocking agents known to theperson skilled in the art from coating technology. The following may bementioned as an example of blocking agents: alcohols, lactams, oximes,malonic esters, alkyl acetoacetates, triazoles, phenols, imidazoles,pyrazoles and amines, such as, for example, butanone oxime,diisopropylamine, 1,2,4-triazole, dimethyl-1,2,4-triazole, imidazole,diethyl malonate, ethyl acetoacetate, acetone oxime,3,5-dimethylpyrazole, ε-caprolactam, N-tert-butylbenzylamine,cyclopentanone carboxyethyl ester or any desired mixtures of theseblocking agents.

Generally, all polyfunctional, isocyanate-reactive compounds which haveon average at least 1.5 isocyanate-reactive groups per molecule can beused. Isocyanate-reactive groups in the context of the presentdisclosure are preferably hydroxy, amino or thio groups; hydroxycompounds can be used in some embodiments. Suitable polyfunctional,isocyanate-reactive compounds are, for example, polyester, polyether,polycarbonate, poly(meth)acrylate and/or polyurethane polyols. In someembodiments, aliphatic, araliphatic or cycloaliphatic di-, tri- orpolyfunctional alcohols having low molecular weights, e.g. havingmolecular weights of less than 500 g/mol, and short chains, e.g.containing 2 to 20 carbon atoms, are also suitable as polyfunctional,isocyanate-reactive compounds. In some embodiments, these may be, forexample, ethylene glycol, diethylene glycol, triethylene glycol,tetraethylene glycol, dipropylene glycol, tripropylene glycol,1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol,2-ethyl-2-butylpropanediol, trimethylpentanediol, positional isomers ofdiethyloctanediol, 1,3-butylene glycol, cyclohexanediol,1,4-cyclohexanedimethanol, 1,6-hexanediol, 1,2- and 1,4-cyclohexanediol,hydrogenated bisphenol A (2,2-bis(4-hydroxycyclohexyl)propane),2,2-dimethyl-3-hydroxy-propionic acid (2,2-dimethyl-3-hydroxypropylester). Examples of suitable triols are trimethylolethane,trimethylolpropane or glycerol. Suitable higher-functional alcohols areditrimethylolpropane, pentaerythritol, dipentaerythritol or sorbitol.Suitable polyester polyols are, for example, linear polyester diols orbranched polyester polyols, as are obtained in a known manner fromaliphatic, cycloaliphatic or aromatic di- or polycarboxylic acids ortheir anhydrides with polyhydric alcohols having an OH functionality of≥2. In some embodiments, di- or polycarboxylic acids or anhydrides aresuccinic, glutaric, adipic, pimelic, suberic, azelaic, sebacic,nonanedicarboxylic, decanedicarboxylic, terephthalic, isophthalic,o-phthalic, tetrahydrophthalic, hexahydrophthalic or trimellitic acidand acid anhydrides such as o-phthalic, trimellitic or succinicanhydride or any desired mixtures thereof with one another. In someembodiments, suitable alcohols are ethanediol, di-, tri- andtetraethylene glycol, 1,2-propanediol, di-, tri- and tetrapropyleneglycol, 1,3-propanediol, butanediol-1,4, butanediol-1,3, butanediol-2,3,pentanediol-1,5, hexanediol-1,6, 2,2-dimethyl-1,3-propanediol,1,4-dihydroxycyclohexane, 1,4-dimethylolcyclohexane, 1,8-octanediol,1,10-decanediol, 1,12-dodecanediol, trimethylolpropane, glycerol or anydesired mixtures thereof with one another. In some embodiments,polyester polyols are based on aliphatic alcohols and mixtures ofaliphatic and aromatic acids and have number average molar massesbetween 500 and 10 000 g/mol and functionalities between 1.8 and 6.1. Insome embodiments, polyester polyols are based on aliphatic diols, suchas butane-1,4-diol, hexane-1,6-diol, neopentyl glycol, ethanediol,propylene glycol, 1,3-butylene glycol, di-, tri-, or polyethyleneglycol, di-, tri- and/or tetrapropylene glycol or mixtures of theabovementioned diols with aliphatic higher-functional alcohols, such astrimethylolpropane and/or pentaerythritol, the proportion of thehigher-functional alcohols preferably accounting for less than 50% byweight (particularly preferably less than 30% by weight), based on thetotal amount of the alcohol used, in combination with aliphatic di- orpolycarboxylic acids or anhydrides such as adipic acid and/or succinicacid, or mixtures of the abovementioned aliphatic polycarboxylic acidsor anhydrides with aromatic polycarboxylic acids or anhydrides, such asterephthalic acid and/or isophthalic acid, the proportion of thearomatic polycarboxylic acids or anhydrides preferably accounting forless than 50% by weight (and particularly preferably less than 30% byweight), based on the total amount of the polycarboxylic acids oranhydrides used. In some embodiments, polyester polyols have numberaverage molar masses between 1000 and 6000 g/mol and functionalitiesbetween 1.9 and 3.3. Polyester polyols may also be based on natural rawmaterials, such as castor oil. It is also possible for the polyesterpolyols to be based on homo- or copolymers of lactones, as canpreferably be obtained by an addition reaction of lactones or lactonemixtures in a ring-opening lactone polymerization, such asbutyrolactone, ε-caprolactone and/or methyl-ε-caprolactone, withhydroxy-functional compounds, such as polyhydric alcohols having an OHfunctionality of ≥2 or polyols having a functionality of greater than1.8, for example of the abovementioned type. In some embodiments,polyols which are used as starters here are polyether polyols having afunctionality of 1.8 to 3.1 and number average molar masses of 200 to4000 g/mol; poly(tetrahydrofurans) having a functionality of 1.9 to 2.2and number average molar masses of 500 to 2000 g/mol (in particular 600to 1400 g/mol) are particularly preferred. In some embodiments, adductsare butyrolactone, ε-caprolactone and/or methyl-ε-caprolactone,ε-caprolactone. In some embodiments, polyester polyols preferably havenumber average molar masses of 400 to 6000 g/mol, or of 800 to 3000g/mol. In some embodiments, OH functionality is 1.8 to 3.5, or 1.9 to2.2.

Suitable polycarbonate polyols are obtainable in a manner known per seby reaction of organic carbonates or phosgene with diols or diolmixtures. In some embodiments, organic carbonates are dimethyl, diethyland diphenyl carbonate. In some embodiments, suitable diols or mixturescomprise the polyhydric alcohols mentioned in the context of thepolyester segments and having an OH functionality of ≥2 preferably1,4-butanediol, 1,6-hexanediol and/or 3-methylpentanediol, or polyesterpolyols can be converted into polycarbonate polyols. In someembodiments, such polycarbonate polyols have number average molar massesof 400 to 4000 g/mol, or of 500 to 2000 g/mol. In some embodiments, theOH functionality of these polyols is 1.8 to 3.2, or 1.9 to 3.0.

In some embodiments, suitable polyether polyols are polyadducts ofcyclic ethers with OH- or NH-functional starter molecules, whichpolyadducts optionally have a block structure. Suitable cyclic ethersare, for example, styrene oxides, ethylene oxide, propylene oxide,tetrahydrofuran, butylene oxide, epichlorohydrin and any desiredmixtures thereof. Starters which may be used are the polyhydric alcoholsmentioned in the context of the polyester polyols and having an OHfunctionality of and primary or secondary amines and amino alcohols. Insome embodiments, polyether polyols are those of the abovementionedtype, exclusively based on propylene oxide or random or block copolymersbased on propylene oxide with further 1-alkylene oxides, the proportionof the 1-alkylene oxide not being higher than 80% by weight. Propyleneoxide homopolymers and random or block copolymers which haveoxyethylene, oxypropylene and/or oxybutylene units can be used in someembodiments, the proportion of the oxypropylene units, based on thetotal amount of all oxyethylene, oxypropylene and oxybutylene units,accounting for at least 20% by weight, preferably at least 45% byweight. Oxypropylene and oxybutylene comprise all respective linear andbranched C3- and C4-isomers. In some embodiments, such polyether polyolshave number average molar masses of 250 to 10 000 g/mol, or of 500 to8500 g/mol, or of 600 to 4500 g/mol. In some embodiments, the OHfunctionality is 1.5 to 4.0, or 1.8 to 3.1, or 1.9 to 2.2.

In some embodiments, matrix forming reactions are enabled or acceleratedby suitable catalysts. For example, cationic epoxy polymerization takesplace rapidly at room temperature by use of BF₃-based catalysts, othercationic polymerizations proceed in the presence of protons,epoxy-mercaptan reactions and Michael additions are accelerated by basessuch as amines, hydrosilylation proceeds rapidly in the presence oftransition metal catalysts such as platinum, and urethane and ureaformation proceed rapidly when tin catalysts are employed. It is alsopossible to use photogenerated catalysts for matrix formation, providedthat steps are taken to prevent polymerization of the photoactivemonomer during the photogeneration.

In some embodiments, the amount of thermoplastic used in a holographicrecording medium described herein is enough that the entire holographicrecording medium effectively acts as a thermoplastic for most processingpurposes. In some embodiments, the binder component of the holographicrecording medium may make up as much as about 5%, or as much as about50%, or as much as about 90% of the holographic recording medium byweight. The amount of any given support matrix in the holographicrecording medium may vary based on clarity, refractive index, meltingtemperature, T_(g), color, birefringence, solubility, etc., of thethermoplastic or thermoplastics that make up the binder component.Additionally, the amount of the support matrix in the holographicrecording medium may vary based on the article's final form, whether itis a solid, a flexible film, or an adhesive.

In one embodiment of the present disclosure, the support matrix includesa telechelic thermoplastic resin, e.g., the thermoplastic polymer may befunctionalized with reactive groups that covalently crosslink thethermoplastic in the support matrix with the polymer formed from thepolymerizable component during grating formation. Such crosslinkingmakes the gratings stored in the thermoplastic holographic recordingmedium very stable, even to elevated temperatures for extended periodsof time.

In some embodiments where a thermoset is formed, the matrix may containfunctional groups that copolymerize or otherwise covalently bond withthe monomer used to form the photopolymer. Such matrix attachmentmethods allow for increased archival life of the recorded holograms.Suitable thermoset systems for used herein are disclosed in to U.S. Pat.No. 6,482,551 (Dhar et al.), incorporated herein by reference.

In some embodiments, the thermoplastic support matrix becomescrosslinked noncovalently with the polymer formed upon grating formationby using a functionalized thermoplastic polymer in the support matrix.Examples of such non-covalent bonding include ionic bonding, hydrogenbonding, dipole-dipole bonding, aromatic pi stacking, etc.

In some embodiments, the polymerizable component of an article of thepresent disclosure includes at least one photoactive polymerizablematerial that can form holographic gratings made of a polymer orco-polymer when exposed to a photoinitiating light source, such as alaser beam that is recording data pages to the holographic recordingmedium. The photoactive polymerizable materials can include any monomer,oligomer, etc., that is capable of undergoing photoinitiatedpolymerization, and which, in combination with the support matrix, meetsthe compatibility requirements of the present disclosure. Suitablephotoactive polymerizable materials include those which polymerize by afree-radical reaction, e.g., molecules containing ethylenic unsaturationsuch as acrylates, methacrylates, acrylamides, methacrylamides, styrene,substituted styrenes, vinyl naphthalene, substituted vinyl naphthalenes,and other vinyl derivatives. Free-radical copolymerizable pair systemssuch as vinyl ether/maleimide, vinyl ether/thiol, acrylate/thiol, vinylether/hydroxy, etc., are also suitable. It is also possible to usecationically polymerizable systems; a few examples are vinyl ethers,alkenyl ethers, allene ethers, ketene acetals, epoxides, etc.Furthermore, anionic polymerizable systems are suitable. It is alsopossible for a single photoactive polymerizable molecule to contain morethan one polymerizable functional group. Other suitable photoactivepolymerizable materials include cyclic disulfides and cyclic esters.Oligomers that may be included in the polymerizable component to form aholographic grating upon exposure to a photoinitiating light sourceinclude oligomers such as oligomeric (ethylene sulfide) dithiol,oligomeric (phenylene sulfide) dithiol, oligomeric (bisphenol A),oligomeric (bisphenol A) diacrylate, oligomeric polyethylene withpendent vinyl ether groups, etc. The photoactive polymerizable materialof the polymerizable component of an article of the present disclosuremay be monofunctional, difunctional, and/or multifunctional.

As described herein, relatively high index contrast is desired in anarticle, whether for improved readout in a recording media or efficientlight confinement in a waveguide. In addition, it is advantageous toinduce this relatively large index change with a small number of monomerfunctional groups, because polymerization of the monomer generallyinduces shrinkage in a material. Such shrinkage has a detrimental effecton the retrieval of data from stored holograms, and also degrades theperformance of waveguide devices such as by increased transmissionlosses or other performance deviations. In some embodiments, loweringthe number of monomer functional groups that must be polymerized toattain the necessary index contrast is therefore desirable. Thislowering is possible by increasing the ratio of the molecular volume ofthe monomers to the number of monomer functional groups on the monomers.This increase is attainable by incorporating into a monomer largerindex-contrasting moieties and/or a larger number of index-contrastingmoieties. For example, if the matrix is composed primarily of aliphaticor other low index moieties and the monomer is a higher index specieswhere the higher index is imparted by a benzene ring, the molecularvolume could be increased relative to the number of monomer functionalgroups by incorporating a naphthalene ring instead of a benzene ring(the naphthalene having a larger volume), or by incorporating one ormore additional benzene rings, without increasing the number of monomerfunctional groups. In this manner, polymerization of a given volumefraction of the monomers with the larger molecular volume/monomerfunctional group ratio would require polymerization of less monomerfunctional groups, thereby inducing less shrinkage. But the requisitevolume fraction of monomer would still diffuse from the unexposed regionto the exposed region, providing the desired refractive index.

The molecular volume of the monomer, however, should not be so large asto slow diffusion below an acceptable rate. Diffusion rates arecontrolled by factors including size of diffusing species, viscosity ofthe medium, and intermolecular interactions. Larger species tend todiffuse more slowly, but it would be possible in some situations tolower the viscosity or make adjustments to the other molecules presentin order to raise diffusion to an acceptable level. Also, as describedherein, it is important to ensure that larger molecules maintaincompatibility with the matrix.

Numerous architectures are possible for monomers containing multipleindex-contrasting moieties. For example, it is possible for the moietiesto be in the main chain of a linear oligomer, or to be substituentsalong an oligomer chain. Alternatively, it is possible for theindex-contrasting moieties to be the subunits of a branched or dendriticlow molecular weight polymer.

In addition to the at least one photoactive polymerizable material, anarticle of the present disclosure may contain a photoinitiator. Thephotoinitiator chemically initiates the polymerization of the at leastone photoactive polymerizable material. The photoinitiator generallyshould offer a source of species that initiate polymerization of theparticular photoactive polymerizable material, e.g., photoactivemonomer. Typically, from about 0.1 to about 20 vol. % photoinitiatorprovides desirable results.

A variety of photoinitiators known to those skilled in the art andavailable commercially are suitable for use as described herein, forexample, those comprising a phosphine oxide group, such asdiphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, disclosed in U.S. Pat.No. 6,780,546 (Trentler et al.), issued Aug. 24, 2004, incorporatedherein by reference. In some embodiments, the photoinitiator issensitive to light at wavelengths available from conventional lasersources, e.g., the blue and green lines of Ar⁺ (458, 488, 514 nm) andHe—Cd lasers (442 nm), the green line of frequency doubled YAG lasers(532 nm), and the red lines of He—Ne (633 nm), Kr⁺ lasers (647 and 676nm), and various diode lasers (290 to 900 nm). In some embodiments, thefree radical photoinitiatorbis(η-5-2,4-cyclopentadien-1-yl)bis[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl]titaniumcan be used. In some embodiments, the free-radical photoinitiator5,7-diiodo-3-butoxy-6-fluorone can be used. In some embodiments, thisphotoinitiator requires a co-initiator. Free-radical photoinitiators ofdye-hydrogen donor systems can also be used. Examples of suitable dyesinclude eosin, rose bengal, erythrosine, and methylene blue, andsuitable hydrogen donors include tertiary amines such as n-methyldiethanol amine. In the case of cationically polymerizable components, acationic photoinitiator is used, such as a sulfonium salt or an iodoniumsalt. These cationic photoinitiator salts absorb predominantly in the UVportion of the spectrum, and are therefore typically sensitized with asensitizer or dye to allow use of the visible portion of the spectrum.An example of an alternative visible cationic photoinitiator is(η₅-2,4-cyclopentadien-1-yl) (η₆-isopropylbenzene)-iron(II)hexafluorophosphate. In some embodiments, photoinitiators used hereinare sensitive to ultraviolet and visible radiation of from about 200 nmto about 800 nm. In some embodiments, other additives can be used in thephotoimageable system, e.g., inert diffusing agents having relativelyhigh or low refractive indices.

In some embodiments, an article described herein may also includeadditives such as plasticizers for altering the properties of thearticle of the present disclosure including the melting point,flexibility, toughness, diffusibility of the monomers and/or oligomers,and ease of processability. Examples of suitable plasticizers includedibutyl phthalate, poly(ethylene oxide) methyl ether,N,N-dimethylformamide, etc. Plasticizers differ from solvents in thatsolvents are typically evaporated whereas plasticizers are meant toremain in the article.

Other types of additives that may be used in the liquid mixture andarticle of the present disclosure are inert diffusing agents havingrelatively high or low refractive indices. Inert diffusing agentstypically diffuse away from the grating being formed, and can be of highor low refractive index. In some embodiments, additives used herein havelow refractive index. In some embodiments, a monomer of high refractiveindex is used with an inert diffusing agent of low refractive index. Insome embodiments, the inert diffusing agent diffuses to the nulls in aninterference pattern. In some embodiments, such diffusion leads to thecontrast of the grating being increased. Other additives that may beused in the liquid mixture and article of the present disclosureinclude: pigments, fillers, nonphotoinitiating dyes, antioxidants,bleaching agents, mold releasing agents, antifoaming agents,infrared/microwave absorbers, surfactants, adhesion promoters, etc.

In some embodiments, the polymerizable component of an article of thepresent disclosure is less than about 20 volume %. In some embodiments,the polymerizable component of an article of the present disclosure maybe less than about 10 volume %, or even less than about 5 volume %. Fordata storage applications, the typical polymerizable component ispresent at about 5 volume %, about 6 volume %, about 7 volume %, about 8volume %, about 9 volume %, about 10 volume %, about 11 volume %, about12 volume %, about 13 volume %, about 14 volume %, or about 15 volume %.In some embodiments, the polymerizable component is present at about 1volume %, about 2 volume %, about 3 volume %, about 4 volume %, about 5volume %, about 6 volume %, about 7 volume %, about 8 volume %, about 9volume %, about 10 volume %, about 11 volume %, about 12 volume %, about13 volume %, about 14 volume %, about 15 volume %, about 16 volume %,about 17 volume %, about 18 volume %, about 19 volume %, or about 20volume %.

An article described herein may be any thickness needed. In someembodiments, the article may be thin for display holography or thick fordata storage. In some embodiments, the article may be, withoutlimitations, a film deposited on a substrate, a free flexible film (forexample a film similar to food wraps), or a hard article requiring nosubstrate (for example similar to a credit card). For data storageapplications, in some embodiments, the article will typically be fromabout 1 to about 1.5 mm in thickness, and is typically in the form of afilm deposited between two substrates with at least one of thesubstrates having an antireflective coating; the article would alsolikely be sealed against moisture and air.

An article of the present disclosure may be heated to form a liquidmixture that is infused into a porous substrate such as glass, cloth,paper, wood, or plastic, then allowed to cool. Such articles would beable to record holograms of a display and/or data nature.

An article of the present disclosure may be made optically flat via theappropriate processes, such as the process described in U.S. Pat. No.5,932,045 (Campbell et al.), issued Aug. 3, 1999, incorporated herein byreference.

By choosing between a wide variety of matrix types to be used in anarticle described herein, reduction or elimination of problems such aswater or humidity can be achieved. In one embodiment, an articledescribed herein may be used to store volatile holograms. Due to theability to control the photopolymer chain length as described herein, aparticular mixture may be tuned to have a very general lifetime for therecorded holograms. Thus, after hologram recording, the holograms may bereadable for a defined time period such as a week, a few months, oryears. Heating the article may also increase such a process of hologramdestruction. In some embodiments, volatile holograms can be used forrental movies, security information, tickets (or season passes), thermalhistory detector, time stamp, and/or temporary personal records, etc.

In some embodiments, an article described herein may be used to recordpermanent holograms. There are several methods to increase thepermanency of recorded holograms. In some embodiments, these methodsinvolve placing functional groups on the matrix that allow for theattachment of photopolymer to the matrix during cure. The attachmentgroups can be vinyl unsaturations, chain transfer sites, orpolymerization retarders such as a BHT derivative. Otherwise, forincreased archival stability of recorded holograms, a multifunctionalmonomer may be used which allows for crosslinking of the photopolymer,thus increasing the entanglement of the photopolymer in the matrix. Insome embodiments, both a multifunctional monomer and a matrix-attachedretarder are used. In this way, the shorter chains that are caused bythe polymerization retarder do not cause loss of archival life.

In addition to the photopolymeric systems described herein, variousphotopolymeric systems may be used in the holographic recording mediumdescribed herein. For example, suitable photopolymeric systems for usein the present disclosure are described in: U.S. Pat. No. 6,103,454(Dhar et al.), U.S. Pat. No. 6,482,551 (Dhar et al.), U.S. Pat. No.6,650,447 (Curtis et al.), U.S. Pat. No. 6,743,552 (Setthachayanon etal.), U.S. Pat. No. 6,765,061 (Dhar et al.), U.S. Pat. No. 6,780,546(Trentler et al.), U.S. Patent Application No. 2003-0206320, publishedNov. 6, 2003, (Cole et al), and U.S. Patent Application No.2004-0027625, published Feb. 12, 2004, incorporated by reference herein.

An article of the present disclosure may be ground, shredded,fragmented, etc. to form a particle material of powder, chips, etc. Theparticle material may be heated at a later time to form a flowableliquid used to make a molded product, a coating to apply to a substrate,etc.

In some embodiments, an article described herein is used to make datastorage devices of various sizes and shapes, as a block of material oras part of a coating that is coated on a substrate.

In some embodiments, the disclosure provides methods for controllingphotopolymerization reactions in the holographic recording medium. Insome embodiments, the disclosure provides methods for reducing,minimizing, diminishing, eliminating, etc., dark reactions in thephotopolymeric systems used in such a holographic recording medium. Insome embodiments, such methods include using one or more of thefollowing: (1) a polymerization retarder; (2) a polymerizationinhibitor; (3) a chain transfer agent; (4) use of metastable reactivecenters; (5) use of light or heat labile phototerminators; (6) use ofphoto-acid generators, photo-base generators or photogenerated radicals;(7) use of polarity or solvation effects; (8) counter ion effects; and(9) changes in photoactive polymerizable material reactivity. Methodsfor controlling radical polymerization are described in “ControlledRadical Polymerization Guide: ATRP, RAFT, NMP,” Aldrich, 2012,incorporated by reference herein (See, e.g., Jakubowski, Tsarevsky,McCarthy, and Matyjaszewsky: “ATRP (Atom Transfer RadicalPolymerization) for Everyone: Ligands and Initiators for the CleanSynthesis of Functional Polymers;” Graj ales: “Tools for PerformingATRP;” Haddleton: “Copper(I)-mediated Living Radical Polymerization inthe Presence of Pyridylmethanimine Ligands;” Haddleton: “TypicalProcedures for Polymerizing via ATRP;” Zhu, Edmondson: “Applying ARGETATRP to the Growth of Polymer Brush Thin Films by Surface-initiatedPolymerization;” Zhu, Edmondson: “ARGET ATRP: Procedure for PMMA PolymerBrush Growth;” “Ligands for ATRP Catalysts;” “Metal Salts for ATRPCatalysts;” “Reversible Addition/Fragmentation Chain TransferPolymerization (RAFT);” Moad, Rizzardo, and Thang: “A Micro Review ofReversible Addition/Fragmentation Chain Transfer (RAFT) Polymerization;”“Concepts and Tools for RAFT Polymerization;” “Typical Procedures forPolymerizing via RAFT;” “Universal/Switchable RAFT Agents forWell-defined Block Copolymers: Agent Selection and Polymerization;”“Polymerization Procedure with Universal/Switchable RAFT Agents;” “RAFTAgents;” “Switchable RAFT Agents;” “Radical Initiators;”“Nitroxide-mediated Polymerization (NMP);” Lee and Wooley: “BlockCopolymer Synthesis Using a Commercially Available Nitroxide-mediatedRadical Polymerization (NMP) Initiator.”

For free radical systems, the kinetics of photopolymerization reactionsare dependent on several variables such as monomer/oligomerconcentration, monomer/oligomer functionality, viscosity of the system,light intensity, photoinitiator type and concentration, the presence ofvarious additives (e.g., chain transfer agents, inhibitors), etc. Thus,for free radical photopolymerization the following steps typicallydescribe the mechanism for formation of the photopolymer:hv+PI→2R*  (initiation reaction)R*+M→M*  (initiation reaction)M*+M→(M)₂*  (propagation reaction)(M)₂*+M→(M)₃*  (propagation reaction)(M)_(n)*+M→(M)_(n+1)*  (propagation reaction)R*+M*→RM  (termination reaction)(M)_(n)*+(M)_(m)*→(M)_(n+m)  (termination reaction)R*+(M)_(m)*→R(M)_(m)  (termination reaction)R*+R*→RR  (termination reaction)

Computing the rates of photoinitiation and polymerization is known inthe art, described for example in U.S. Pat. No. 7,704,643, incorporatedherein by reference. The rate of initiation depends on the number ofradicals generated by the photoinitiator (n=2 for many free radicalinitiators, n=1 for many cationic initiators), the quantum yield forinitiation (typically less than 1), the intensity of absorbed light,incident light intensity, the concentration of photoinitiator, the molarabsorptivity of the initiator at the wave length of interest, and thethickness of the system. The rate of polymerization depends on thekinetic rate constant for polymerization (k_(p)), the monomerconcentration, and the kinetic rate constant for termination (k_(t)). Insome embodiments, it is assumed that the light intensity does not varyappreciably through the medium. In some embodiments, the quantumefficiency of initiation for free radical photoinitiators is greatlyaffected by monomer concentration, viscosity, and rate of initiationwhen monomer concentration is below 0.1 M, which is in some embodimentsthe regime for a two-component type photopolymer holographic medium.Thus, in some embodiments, the following dependencies are found todecrease the quantum yield for initiation: higher viscosities, lowermonomer concentration, and higher initiation rates (from increasedintensity, higher molar absorptivity, etc.).

When a polymerization retarder/inhibitor Z—Y is added, the followingadditional steps can occur (where X* represents any radical):X*+Z-Y→X-Y+Z*  (termination reaction)Z*+X*→Z—X  (termination reaction).

Assuming that transfer to the retarder/inhibitor is high relative toother termination reactions, the rate of polymerization further dependson the concentration of the inhibitor and the rate constant of thetermination with retarder/inhibitor (k_(z)). The polymerization rate isalso further dependent on the 1^(st) power of the initiation rate. Theratio of k_(z)/k_(p) is referred to as the inhibitor constant (e.g.,lower case z). Values much greater than about 1 represent an inhibitoryeffect, whereas values of about 1 or less represent retarding effects.Values much less than about 1 represent little effect on thepolymerization rate.

The difference between a polymerization inhibitor and a polymerizationretarder frequently depends on the particular polymerizable componentinvolved. For example, nitrobenzene only mildly retards radicalpolymerization of methyl acrylate, yet, nitrobenzene inhibits radicalpolymerization of vinyl acetate. Thus, it is possible to find agentsthat are typically considered as inhibitors that would also function asretarders for the purposes of the present disclosure. Inhibitorconstants z for various polymerization retarders/inhibitors with variouspolymer systems are known in the art and described for example in U.S.Pat. No. 7,704,643, incorporated herein by reference.

Suitable polymerization retarders and inhibitors for use herein includebut are not limited to one or more of the following: for free radicalpolymerizations, various phenols including butylated hydroxytoluenes(BHT) such as 2,6-di-t-butyl-p-cresol, p-methoxyphenol,diphenyl-p-benzoquinone, benzoquinone, hydroquinone, pyrogallol,resorcinol, phenanthraquinone, 2,5-toluquinone, benzylaminophenol,p-dihydroxybenzene, 2,4,6-trimethylphenol, etc.; various nitrobenzenesincluding o-dinitrobenzene, p-dinitrobenzene, m-dinitrobenzene, etc.;N-phenyl-1-naphthylamine, N-phenyl-2-naphthylamine, cupferron,phenothiazine, tannic acid, p-nitrosamine, chloranil, aniline, hinderedanilines, ferric chloride, cupric chloride, triethylamine, etc. Thesepolymerization retarders and inhibitors can be used individually (e.g.,a single retarder) or in combinations of two or more, e.g., a pluralityof retarders. The same principles can be applied to ionicpolymerizations. For example, it is known that chloride anions canbehave as retarders or inhibitors for cationic polymerizations,depending on both the monomer type and the concentration of the chlorideanions. Typically, functionalities that are basic or mildly nucleophilicbehave as retarders and inhibitors for cationic polymerizations; whereasfor anionic polymerizations, slightly acidic and mildly electrophilicfunctionalities behave as retarders and inhibitors.

In some embodiments, polymerization reactions involving bothpolymerization retarders and inhibitors should lead to terminationreactions. If reinitiation occurs to any appreciable degree, then theagent is typically considered a chain transfer agent. For example,triethylamine can be used as a chain transfer agent since it is alsocapable of reinitiating some radical polymerizations; however, when thereinitiation is slow compared to termination reactions, then even chaintransfer agents can be considered potential polymerization retarders orinhibitors for the purposes of the present disclosure. Suitable chaintransfer agents for use herein include but are not limited to:triethylamine, thioethers, compounds having carbonate groups, ethers,toluene derivatives, allyl ethers, etc. Chain transfer agents that aremildly retarding can be desirable because these can be incorporated intothe matrix and enable attachment of the photopolymer and photoinitiatorradicals to the matrix.

In some embodiments, after the first several exposures in recordingmultiple holograms, the amount of polymerization inhibitor present inthe medium can be reduced. Conversely, with the use of a polymerizationretarder, only small amounts of the retarder are reacted during anygiven exposure. Therefore, the concentration of the polymerizationretarder can potentially decrease substantially linearly and incorrelation to the reduction in monomer concentration. Thus, even latein the exposure schedule, there is enough retarder to prevent bothpolymerization after an exposure and polymerization in low lightintensity areas. Effectively, the polymerization retarder serves as achain length limiter. Ideally, the ratio of polymerization retarder topolymerizable material (e.g., monomer) stays nearly constant throughoutthe exposure schedule. In such a scenario, the chain length (degree ofpolymerization), potentially, stays essentially the same throughout theexposure schedule, leading to a substantially linear response for numberof exposures versus time period for each exposure. The use ofretarders/inhibitors/chain transfer agents is not limited to radicalpolymerizations, and is applicable as well to ionic chainpolymerizations.

In addition to retarders, inhibitors and/or chain transfer agents,metastable reactive centers and light labile phototerminators can alsobe used to control polymerization reactions described herein of theappropriate reactivity. For example, nitroxyl radicals can be added as ametastable reactive center. Nitroxyl radicals create pseudo-livingradical polymerizations with certain monomers. Thus, the nitroxylradical initially behaves as a terminating agent (such as an inhibitor),however, depending on the temperature at which the polymerization iscarried out, the termination is reversible. In such scenarios, chainlength can be controlled by changing the recording temperature. Thus, itis possible to record holograms at an elevated temperature and then coolto room temperature to prevent further polymerizations. Additionally, itis possible to record at room temperature, thus terminating all chainsquickly like an inhibitor, and then to heat the sample to enable theaddition of new photoactive monomer to all the gratings at the sametime. In this other scenario, there is an advantage gained from thepolymerization of all gratings occurring at a single time in that Braggdetuning would be uniform for all gratings involved. Other potentialmetastable reactive center include triphenylmethyl radicals,dithioesters are typically used in Reversible Addition-Fragmentationchain Transfer (RAFT) polymerizations, that can behave as appropriatemetastable reactive centers, etc. As for ionic polymerizations, thereare stable ions that are able to perform the same function, as theexample nitroxyl radicals above.

Use of a light labile phototerminator provides the ability to controlthe activity of the reactive species with light (as opposed to heat asdescribed above). A light labile phototerminator is any molecule capableof undergoing reversible termination reactions using a light source. Forexample, certain cobaltoxime complexes can be used to photoinitiateradical polymerizations, and yet, also terminate the same radicalpolymerizations. Dithioesters are also suitable as light labilephototerminators because they have the ability to reversibly formradicals with appropriate wavelengths of light. Under the appropriateconditions and with appropriate monomers (such as styrenes andacrylates), it is possible to restart the polymerization by irradiatingwith a photoinitiating light source (e.g., recording light). Thus, aslong as a given volume is exposed to a photoinitiating light source,radical polymerization continues, whereas when the photoinitiating lightis off or absent, the polymerizations are terminated. Metastablereactive centers and light labile phototerminators can also be used tocontrol ionic (e.g., cationic or anionic initiated) polymerizationreaction systems according to the present disclosure.

For ionic chain reactions (e.g., cationic and anionic initiatedpolymerization reactions), counter ion and solvent effects can be usedto control polymerization by terminating the reactive center. Ionicsystems are sensitive to solvent conditions because the solvent (or thesupport matrix) determines the proximity of the counter ion to thereactive center. For instance, in a nonpolar medium the counter ion willbe very closely associated with the reactive center; in a polar mediumthe counter ion may become freely dissociated. The proximity of thecounter ion can determine polymerization rate as well as the potentialfor collapse with the counter ion (depending on the counter ion used).For example, if one uses a cationic polymerization with a nonpolarsupport matrix and chloride anion as the counter ion, there is a betterprobability of terminating the reaction due to collapse of the counterion. Thus, in this way, ionic polymerizations can be terminated in acontrolled manner, since choice of support matrix and counter ionsallows one to determine the likelihood of collapse versus theprobability of propagation.

Certain monomer mixtures can also behave in a manner that can controlthe degree or rate of polymerization. For example, if a small amount ofalpha methyl styrene is present in an acrylate polymerization, theacrylate will add into the alpha methyl styrene and the styrene will notsubstantially reinitiate polymerization of the acrylate, e.g., the alphamethyl styrene retards the rate of acrylate polymerization.Additionally, the alpha methyl styrene is slow to polymerize withitself, and thus behaves as a polymerization retarder/inhibitor eventhough it is a comonomer. In the case of ionic polymerizations; using,for example, vinyl anisole in a cationic vinyl ether polymerizationresults in retarded rates of polymerization because the vinyl anisoledoes not efficiently reinitiate vinyl ether polymerization.

Volume Holograms, Photosensitive Polymers, and Devices Thereof

In some embodiments, the present disclosure relates to recordingmaterials for volume holograms, where the recording material ischaracterized by a thickness and includes one or more compoundsdescribed herein.

The disclosure provides a resin mixture including a partially orcompletely polymerized or crosslinked polymer matrix; a polymerprecursor including a monomer M; and a group of Formula I: where IN isan initiating moiety optionally linked to, or part of, the matrix, -[M]-is a polymerized monomer, and x is an integer from 0 to 50. In someembodiments, IN is linked to, or part of, the matrix, as in Formula II.In some embodiments, IN includes an alkyl amine or a carboxyl group. Insome embodiments, x is 0, as in Formula III, and where

is an optional link to the matrix.

In some embodiments of a resin mixture described herein, the group ofFormula I, Formula II, or Formula III is selected from the groups ofFormulas 101 to 107, where

is an optional link to the matrix.

In some embodiments of a resin mixture described herein, M is selectedfrom an optionally substituted acrylate, an optionally substitutedmethacrylate, an optionally substituted acrylamide, an optionallysubstituted methacrylamide, an optionally substituted styrene, anoptionally substituted vinyl derivative, and an optionally substitutedallyl derivative.

In some embodiments of a resin mixture described herein, x is at least1, and -[M]- is selected from a polymerized optionally substitutedacrylate, a polymerized optionally substituted methacrylate, apolymerized optionally substituted acrylamide, a polymerized optionallysubstituted methacrylamide, a polymerized optionally substitutedstyrene, a polymerized optionally substituted vinyl derivative, and apolymerized optionally substituted allyl derivative.

In some embodiments of a resin mixture described herein, any one ofFormulas I, II, and 101 to 106 is selected from the groups of Formulas1001 to 1011, where x is at least 1; R¹ is selected from hydrogen,optionally substituted alkyl, optionally substituted heteroalkyl,optionally substituted alkenyl, optionally substituted alkynyl,optionally substituted cycloalkyl, optionally substitutedheterocycloalkyl, optionally substituted aryl, optionally substitutedarylalkyl, optionally substituted heteroaryl, and optionally substitutedheteroarylalkyl; R² is independently a group of one, two, three, or fourindependently selected substituents, or no substituent, each substituentindependently including one or more groups selected from optionallysubstituted alkyl, optionally substituted heteroalkyl, optionallysubstituted alkenyl, optionally substituted alkynyl, optionallysubstituted cycloalkyl, optionally substituted heterocycloalkyl,optionally substituted aryl, optionally substituted arylalkyl,optionally substituted heteroaryl, optionally substitutedheteroarylalkyl, hydroxy, halo, cyano, trifluoromethyl,trifluoromethoxy, nitro, trimethylsilanyl, —OR^(a), —SR^(a),—OC(O)—R^(a), —N(R^(a))₂, —C(O)R^(a), —C(O)OR^(a), —OC(O)OR^(a),—OC(O)N(R^(a))₂, —C(O)N(R^(a))₂, —N(R^(a))C(O)OR^(a),—N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂, N(R^(a))C(NR^(a))N(R^(a))₂,—N(R^(a))S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)OR^(a),—S(O)_(t)R^(a), —S(O)_(t)N(R^(a))₂, —S(O)_(t)N(R^(a))C(O)R^(a),(O)P(OR^(a))₃, (S)P(OR^(a))₃, and —(O)P(OR^(a))₂; R³ is selected fromoptionally substituted alkyl, optionally substituted heteroalkyl,optionally substituted alkenyl, optionally substituted alkynyl,optionally substituted cycloalkyl, optionally substitutedheterocycloalkyl, optionally substituted aryl, optionally substitutedarylalkyl, optionally substituted heteroaryl, optionally substitutedheteroarylalkyl, trifluoromethyl, trifluoromethoxy, nitro,trimethylsilanyl, —OR^(a), —SR^(a), —OC(O)—R^(a), —N(R^(a))₂,—C(O)R^(a), —C(O)OR^(a), —OC(O)OR^(a), —OC(O)N(R^(a))₂, —C(O)N(R^(a))₂,—N(R^(a))C(O)OR^(a), —N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂,N(R^(a))C(NR^(a))N(R^(a))₂, —N(R^(a))S(O)_(t)R^(a), —S(O)_(t)OR^(a),—S(O)_(t)R^(a), —S(O)_(t)N(R^(a))₂, —S(O)_(t)N(R^(a))C(O)R^(a),—O(O)P(OR^(a))₂, and —O(S)P(OR^(a))₂; t is 1 or 2; and R^(a) isindependently selected from hydrogen, optionally substituted alkyl,optionally substituted heteroalkyl, optionally substituted alkenyl,optionally substituted alkynyl, optionally substituted cycloalkyl,optionally substituted heterocycloalkyl, optionally substituted aryl,optionally substituted arylalkyl, optionally substituted heteroaryl, andoptionally substituted heteroarylalkyl.

In some embodiments of a resin mixture described herein, the polymermatrix includes a polyurethane fragment. In some embodiments, thepolyurethane is derived from an isocyanate selected from butylenediisocyanate, hexamethylene diisocyanate (HDI), isophorone diisocyanate(IPDI), 1,8-diisocyanato-4-(isocyanatomethyl)octane,2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylenediisocyanate, isomeric bis(4,4′-isocyanatocyclohexyl)methane and anyisomer thereof, isocyanatomethyl-1,8-octane diisocyanate,1,4-cyclohexylene diisocyanate, isomeric cyclohexanedimethylenediisocyanates, 1,4-phenylene diisocyanate, 2,4-toluene diisocyanate,2,6-toluene diisocyanate, 1,5-naphthylene diisocyanate,2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate,and triphenylmethane 4,4′,4″-triisocyanate.

In some embodiments of a resin mixture described herein, a group of anyof Formulas I, II, 101 to 106, and 1001 to 1011, is heat labile. In someembodiments of a resin mixture described herein, a group of any ofFormulas I, II, 101 to 106, and 1001 to 1011, is chemically reactive.

In some embodiments, the disclosure provides a recording material forwriting a volume Bragg grating, the material including a transparentsupport and any resin mixture described herein. In some embodiments, thematerial has a thickness of between 1 μm and 500 μm.

In some embodiments, the disclosure provides a method of recording avolume Bragg grating on any recording material described herein, thematerial including a resin mixture including a partially or completelypolymerized or crosslinked polymer matrix, a polymer precursor includinga monomer M, an initiator precursor Pr—IN optionally linked to, or partof, the matrix, a nitroxide, and an optional sensitizer; the methodincluding subjecting the material to a source of light to generate inthe resin mixture a group of Formula I, where -[M]- is a polymerizedmonomer, x is an integer from 0 to 50, and the group of Formula I isanisotropically distributed throughout the material. In someembodiments, the portions of material having a high concentration ofFormula I form a virtual Bragg grating, where the grating ischaracterized by a Q parameter equal to or greater than 10, where

$Q = \frac{2{\pi\lambda}_{0}d}{n_{0}\Lambda^{2}}$and where λ₀ is a recording wavelength, d is the thickness of therecording material, n₀ is a refractive index of the recording material,and Λ is a grating constant. In some embodiments, the method furtherincludes heating the material to a temperature between about 50° C. andabout 125° C. In some embodiments, the method further includes ableaching step. In some embodiments, the bleaching step develops thevirtual Bragg grating into an actual Bragg grating. In some embodiments,IN is linked to, or part of, the matrix, as in Formula II. In someembodiments, IN includes an alkyl amine or a carboxyl group. In someembodiments, x is 0, as in Formula III, and where

is an optional link to the matrix. In some embodiments, the group ofFormula I, Formula II, or Formula III is selected from the groups ofFormulas 101 to 107, where

is an optional link to the matrix.

As shown in FIG. 8 , any method described herein can include one or moresteps. In some embodiments, radicals are generated at once, but areimmediately quenched. In some embodiments, little to no grating growthoccurs during the exposure, which leads to low levels of haze. Anitroxide described herein, for example TEMPO, cannot initiatepolymerization, so polymerization only occurs in areas where alkoxyamineis formed, and, in some embodiments, chain transfer and terminationreactions are eliminated. In some embodiments, as long as eitherinitiating site or nitroxide is bound to matrix, polymer cannot diffuseaway from exposure area, resulting in large Δn. In some embodiments,since diffusion is no longer as limiting, spatial frequency performanceis potentially improved. In some embodiments, a method can include aninitiation step, FIG. 8 , A), where a sensitizer S reacts with aco-initiator CI, to provide a radical. In some embodiments, this radicalcan be an alkyl amine radical. In some embodiments, a method can includea quenching step, FIG. 8 , B). In some embodiments, a radicalco-initiator can be quenched by a nitroxide. In some embodiments, theradical co-initiator may react first with a one or more monomermolecules, and then be quenched by a nitroxide. In some embodiments,upon heat activation, a quenched polymer or oligomer P—ON molecule maybe heat activated, where the nitroxide moiety is radically cleaved, andthe resulting radical polymer or oligomer further polymerizes withmonomer molecules. Similar steps have been described in the literature,for example in ACS Macro Lett, 2016, 946, referenced herein in itsentirety.

Nitroxides useful in any methods described herein are known in the art,or can be designed by one of skill in the art. In some embodiments,nitroxide and nitroxide containing initiators are selected from any ofthe following:

In some embodiments, M is selected from an optionally substitutedacrylate, an optionally substituted methacrylate, an optionallysubstituted acrylamide, an optionally substituted methacrylamide, anoptionally substituted styrene, an optionally substituted vinylderivative, and an optionally substituted allyl derivative. In someembodiments, x is at least 1, and -[M]- is selected from a polymerizedoptionally substituted acrylate, a polymerized optionally substitutedmethacrylate, a polymerized optionally substituted acrylamide, apolymerized optionally substituted methacrylamide, a polymerizedoptionally substituted styrene, a polymerized optionally substitutedvinyl derivative, and a polymerized optionally substituted allylderivative. In some embodiments, any one of Formulas I, II, and 101 to106 is selected from the groups of Formulas 1001 to 1011, where x is atleast 1; R¹ is selected from hydrogen, optionally substituted alkyl,optionally substituted heteroalkyl, optionally substituted alkenyl,optionally substituted alkynyl, optionally substituted cycloalkyl,optionally substituted heterocycloalkyl, optionally substituted aryl,optionally substituted arylalkyl, optionally substituted heteroaryl, andoptionally substituted heteroarylalkyl; R² is independently a group ofone, two, three, or four independently selected substituents, or nosubstituent, each substituent independently including one or more groupsselected from optionally substituted alkyl, optionally substitutedheteroalkyl, optionally substituted alkenyl, optionally substitutedalkynyl, optionally substituted cycloalkyl, optionally substitutedheterocycloalkyl, optionally substituted aryl, optionally substitutedarylalkyl, optionally substituted heteroaryl, optionally substitutedheteroarylalkyl, hydroxy, halo, cyano, trifluoromethyl,trifluoromethoxy, nitro, trimethylsilanyl, —OR^(a), —SR^(a),—OC(O)—R^(a), —N(R^(a))₂, —C(O)R^(a), —C(O)OR^(a), —OC(O)OR^(a),—OC(O)N(R^(a))₂, —C(O)N(R^(a))₂, —N(R^(a))C(O)OR^(a),—N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂, —N(R^(a))C(NR^(a))N(R^(a))₂,—N(R^(a))S(O)_(t)R^(a), —S(O)_(t)OR^(a), —S(O)_(t)R^(a),—S(O)_(t)N(R^(a))₂, —S(O)_(t)N(R^(a))C(O)R^(a), (O)P(OR^(a))₃,(S)P(OR^(a))₃, —(O)P(OR^(a))₂, —(S)P(OR^(a))₂, —O(O)P(OR^(a))₂, and—O(S)P(OR^(a))₂ (where t is 1 or 2); R³ is selected from optionallysubstituted alkyl, optionally substituted heteroalkyl, optionallysubstituted alkenyl, optionally substituted alkynyl, optionallysubstituted cycloalkyl, optionally substituted heterocycloalkyl,optionally substituted aryl, optionally substituted arylalkyl,optionally substituted heteroaryl, optionally substitutedheteroarylalkyl, trifluoromethyl, trifluoromethoxy, nitro,trimethylsilanyl, —OR^(a), —SR^(a), —OC(O)—R^(a), —N(R^(a))₂,—C(O)R^(a), —C(O)OR^(a), —OC(O)OR^(a), —OC(O)N(R^(a))₂, —C(O)N(R^(a))₂,—N(R^(a))C(O)OR^(a), —N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂,—N(R^(a))C(NR^(a))N(R^(a))₂, —N(R^(a))S(O)_(t)R^(a), —S(O)_(t)OR^(a),—S(O)_(t)R^(a), —S(O)_(t)N(R^(a))₂, —S(O)_(t)N(R^(a))C(O)R^(a),(O)P(OR^(a))₃, (S)P(OR^(a))₃, —(O)P(OR^(a))₂, —(S)P(OR^(a))₂,—O(O)P(OR^(a))₂, and —O(S)P(OR^(a))₂ (where t is 1 or 2); and R^(a) isindependently selected from hydrogen, optionally substituted alkyl,optionally substituted heteroalkyl, optionally substituted alkenyl,optionally substituted alkynyl, optionally substituted cycloalkyl,optionally substituted heterocycloalkyl, optionally substituted aryl,optionally substituted arylalkyl, optionally substituted heteroaryl, andoptionally substituted heteroarylalkyl.

In some embodiments, the polymer matrix includes a polyurethanefragment. In some embodiments, the polyurethane is derived from anisocyanate selected from butylene diisocyanate, hexamethylenediisocyanate (HDI), isophorone diisocyanate (IPDI),1,8-diisocyanato-4-(isocyanatomethyl)octane,2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylenediisocyanate, isomeric bis(4,4′-isocyanatocyclohexyl)methane and anyisomer thereof, isocyanatomethyl-1,8-octane diisocyanate,1,4-cyclohexylene diisocyanate, isomeric cyclohexanedimethylenediisocyanates, 1,4-phenylene diisocyanate, 2,4-toluene diisocyanate,2,6-toluene diisocyanate, 1,5-naphthylene diisocyanate,2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate,and triphenylmethane 4,4′,4″-triisocyanate.

The following clauses describe certain embodiments.

Clause 1: a resin mixture comprising: a partially or completelypolymerized or crosslinked polymer matrix; a polymer precursorcomprising a monomer M; an initiator species IN; and a free radicalcompound.

Clause 2: the resin mixture of clause 1, wherein a portion of theinitiator species IN is linked to the matrix or to a portion of thematrix, as in Formula A:

Clause 3: the resin mixture of clause 1 or clause 2, wherein theinitiator species IN comprises an alkyl-amine moiety.

Clause 4: the resin mixture of clause 3, wherein the alkyl is methyl.

Clause 5: the resin mixture of any one of clauses 1 to 4, wherein thefree radical compound comprises a moiety of Formula B:

Clause 6: the resin mixture of any one of clauses 1 to 5, wherein thefree radical compound is selected from:

Clause 7: the resin mixture of any one of clauses 1 to 6, wherein themonomer M is selected from an optionally substituted acrylate, anoptionally substituted methacrylate, an optionally substitutedacrylamide, an optionally substituted methacrylamide, an optionallysubstituted styrene, an optionally substituted vinyl derivative, and anoptionally substituted allyl derivative.

Clause 8: the resin mixture of any one of clauses 1 to 7, wherein thepartially or completely polymerized or crosslinked polymer matrixcomprises a polyurethane.

Clause 9: a resin mixture comprising: a partially or completelypolymerized or crosslinked polymer matrix; a polymer precursorcomprising a monomer M; and a group of Formula I:

wherein IN is an initiating moiety optionally linked to, or part of, thematrix, -[M]- is a polymerized monomer, and x is an integer from 0 to50.

Clause 10: the resin mixture of clause 9, wherein IN is linked to, orpart of, the matrix, as in Formula II:

Clause 11: the resin mixture of clause 9 or clause 10, wherein INcomprises an alkyl amine or a carboxyl group.

Clause 12: the resin mixture of any one of clauses 9 to 11, wherein x is0, as in Formula III:

and wherein

is an optional link to the matrix.

Clause 13: the resin mixture of any one of clauses 9 to 12, wherein thegroup of Formula I, Formula II, or Formula III is selected from thegroups of Formulas 101 to 107, wherein

is an optional link to the matrix:

Clause 14: the resin mixture of any one of clauses 9 to 13, wherein M isselected from an optionally substituted acrylate, an optionallysubstituted methacrylate, an optionally substituted acrylamide, anoptionally substituted methacrylamide, an optionally substitutedstyrene, an optionally substituted vinyl derivative, and an optionallysubstituted allyl derivative.

Clause 15: the resin mixture of any one of clauses 9, 10, 11, or 13,wherein xis at least 1, and -[M]- is selected from a polymerizedoptionally substituted acrylate, a polymerized optionally substitutedmethacrylate, a polymerized optionally substituted acrylamide, apolymerized optionally substituted methacrylamide, a polymerizedoptionally substituted styrene, a polymerized optionally substitutedvinyl derivative, and a polymerized optionally substituted allylderivative.

Clause 16: the resin mixture of any one of clauses 9, 10, 11, 13, 14, or15, wherein any one of Formulas I, II, and 101 to 106 is selected fromthe groups of Formulas 1001 to 1011:

wherein: x is at least 1; R¹ is selected from hydrogen, optionallysubstituted alkyl, optionally substituted heteroalkyl, optionallysubstituted alkenyl, optionally substituted alkynyl, optionallysubstituted cycloalkyl, optionally substituted heterocycloalkyl,optionally substituted aryl, optionally substituted arylalkyl,optionally substituted heteroaryl, and optionally substitutedheteroarylalkyl; R² is independently a group of one, two, three, or fourindependently selected substituents, or no substituent, each substituentindependently comprising one or more groups selected from optionallysubstituted alkyl, optionally substituted heteroalkyl, optionallysubstituted alkenyl, optionally substituted alkynyl, optionallysubstituted cycloalkyl, optionally substituted heterocycloalkyl,optionally substituted aryl, optionally substituted arylalkyl,optionally substituted heteroaryl, optionally substitutedheteroarylalkyl, hydroxy, halo, cyano, trifluoromethyl,trifluoromethoxy, nitro, trimethylsilanyl, —OR^(a), —SR^(a),—OC(O)—R^(a), —N(R^(a))₂, —C(O)R^(a), —C(O)OR^(a), —OC(O)OR^(a),—OC(O)N(R^(a))₂, —C(O)N(R^(a))₂, —N(R^(a))C(O)OR^(a),—N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂, N(R^(a))C(NR^(a))N(R^(a))₂,—N(R^(a))S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)OR^(a),—S(O)_(t)N(R^(a))₂, —S(O)_(t)N(R^(a))C(O)R^(a), (O)P(OR^(a))₃,(S)P(OR^(a))₃, and —(O)P(OR^(a))₂; R³ is selected from optionallysubstituted alkyl, optionally substituted heteroalkyl, optionallysubstituted alkenyl, optionally substituted alkynyl, optionallysubstituted cycloalkyl, optionally substituted heterocycloalkyl,optionally substituted aryl, optionally substituted arylalkyl,optionally substituted heteroaryl, optionally substitutedheteroarylalkyl, trifluoromethyl, trifluoromethoxy, nitro,trimethylsilanyl, —OR^(a), —SR^(a), —OC(O)—R^(a), —N(R^(a))₂,—C(O)R^(a), —C(O)OR^(a), —OC(O)OR^(a), —OC(O)N(R^(a))₂, —C(O)N(R^(a))₂,—N(R^(a))C(O)OR^(a), —N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂,N(R^(a))C(NR^(a))N(R^(a))₂, —N(R^(a))S(O)_(t)R^(a), —S(O)_(t)OR^(a),—S(O)_(t)N(R^(a))₂, —S(O)_(t)N(R^(a))C(O)R^(a), —O(O)P(OR^(a))₂, and—O(S)P(OR^(a))₂; t is 1 or 2; and R^(a) is independently selected fromhydrogen, optionally substituted alkyl, optionally substitutedheteroalkyl, optionally substituted alkenyl, optionally substitutedalkynyl, optionally substituted cycloalkyl, optionally substitutedheterocycloalkyl, optionally substituted aryl, optionally substitutedarylalkyl, optionally substituted heteroaryl, and optionally substitutedheteroarylalkyl.

Clause 17: the resin mixture of any one of clauses 9 to 16, wherein thepolymer matrix comprises a polyurethane fragment.

Clause 18: the resin mixture of clause 17, wherein the polyurethane isderived from an isocyanate selected from butylene diisocyanate,hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI),1,8-diisocyanato-4-(isocyanatomethyl)octane,2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylenediisocyanate, isomeric bis(4,4′-isocyanatocyclohexyl)methane and anyisomer thereof, isocyanatomethyl-1,8-octane diisocyanate,1,4-cyclohexylene diisocyanate, isomeric cyclohexanedimethylenediisocyanates, 1,4-phenylene diisocyanate, 2,4-toluene diisocyanate,2,6-toluene diisocyanate, 1,5-naphthylene diisocyanate,2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate,and triphenylmethane 4,4′,4″-triisocyanate.

Clause 19: the resin mixture of any one of clauses 9 to 18, wherein thegroup of Formula I is heat labile.

Clause 20: the resin mixture of any one of clauses 9 to 19, wherein thegroup of Formula I is chemically reactive.

Clauses 21: a recording material for writing a volume Bragg grating, thematerial comprising a transparent support and a resin mixture of any oneof clauses 1 to 20.

Clause 22: the recording material of clause 21, wherein the material hasa thickness of between 1 μm and 500 μm.

Clause 23: a volume Bragg grating recorded on the recording material ofclaim 21 or claim 22, wherein the grating is characterized by a Qparameter equal to or greater than 5, wherein

$Q = \frac{2{\pi\lambda}_{0}d}{n_{0}\Lambda^{2}}$

wherein λ₀ is a recording wavelength, d is the thickness of therecording material, n₀ is a refractive index of the recording material,and Λ is a grating constant.

In some embodiments, the Q parameter is equal to or greater than 1. Insome embodiments, the Q parameter is equal to or greater than 2. In someembodiments, the Q parameter is equal to or greater than 3. In someembodiments, the Q parameter is equal to or greater than 4. In someembodiments, the Q parameter is equal to or greater than 5. In someembodiments, the Q parameter is equal to or greater than 6. In someembodiments, the Q parameter is equal to or greater than 7. In someembodiments, the Q parameter is equal to or greater than 8. In someembodiments, the Q parameter is equal to or greater than 9. In someembodiments, the Q parameter is equal to or greater than 10. In someembodiments, the Q parameter is equal to or greater than 11. In someembodiments, the Q parameter is equal to or greater than 12. In someembodiments, the Q parameter is equal to or greater than 13. In someembodiments, the Q parameter is equal to or greater than 14. In someembodiments, the Q parameter is equal to or greater than 15.

Clause 24: a polymeric material comprising the resin mixture of any oneof clauses 9 to 20, wherein the group of Formula I is anisotropicallydistributed throughout the material.

Clause 25: the polymeric material of clause 24, wherein the portions ofmaterial having a high concentration of Formula I form a virtual Bragggrating, wherein the grating is characterized by a Q parameter equal toor greater than 5, wherein

$Q = \frac{2{\pi\lambda}_{0}d}{n_{0}\Lambda^{2}}$

and wherein λ₀ is a recording wavelength, d is the thickness of therecording material, n₀ is a refractive index of the recording material,and Λ is a grating constant.

In some embodiments, the Q parameter is equal to or greater than 1. Insome embodiments, the Q parameter is equal to or greater than 2. In someembodiments, the Q parameter is equal to or greater than 3. In someembodiments, the Q parameter is equal to or greater than 4. In someembodiments, the Q parameter is equal to or greater than 5. In someembodiments, the Q parameter is equal to or greater than 6. In someembodiments, the Q parameter is equal to or greater than 7. In someembodiments, the Q parameter is equal to or greater than 8. In someembodiments, the Q parameter is equal to or greater than 9. In someembodiments, the Q parameter is equal to or greater than 10. In someembodiments, the Q parameter is equal to or greater than 11. In someembodiments, the Q parameter is equal to or greater than 12. In someembodiments, the Q parameter is equal to or greater than 13. In someembodiments, the Q parameter is equal to or greater than 14. In someembodiments, the Q parameter is equal to or greater than 15.

Clause 26: a volume Bragg grating obtained by heating the polymericmaterial of claim 25.

Clause 27: a method of recording a volume Bragg grating on a recordingmaterial comprising a resin mixture comprising a partially or completelypolymerized or crosslinked polymer matrix, a polymer precursorcomprising a monomer M, an initiator precursor Pr—IN optionally linkedto, or part of, the matrix, a nitroxide, and an optional sensitizer; themethod comprising: subjecting the material to a source of light togenerate in the resin mixture a group of Formula I:

wherein -[M]- is a polymerized monomer, x is an integer from 0 to 50,and the group of Formula I is anisotropically distributed throughout thematerial.

Clause 28: the method of clause 27, wherein the portions of materialhaving a high concentration of Formula I form a virtual Bragg grating,wherein the grating is characterized by a Q parameter equal to orgreater than 5, wherein

$Q = \frac{2{\pi\lambda}_{0}d}{n_{0}\Lambda^{2}}$

and wherein λ₀ is a recording wavelength, d is the thickness of therecording material, n₀ is a refractive index of the recording material,and Λ is a grating constant.

In some embodiments, the Q parameter is equal to or greater than 1. Insome embodiments, the Q parameter is equal to or greater than 2. In someembodiments, the Q parameter is equal to or greater than 3. In someembodiments, the Q parameter is equal to or greater than 4. In someembodiments, the Q parameter is equal to or greater than 5. In someembodiments, the Q parameter is equal to or greater than 6. In someembodiments, the Q parameter is equal to or greater than 7. In someembodiments, the Q parameter is equal to or greater than 8. In someembodiments, the Q parameter is equal to or greater than 9. In someembodiments, the Q parameter is equal to or greater than 10. In someembodiments, the Q parameter is equal to or greater than 11. In someembodiments, the Q parameter is equal to or greater than 12. In someembodiments, the Q parameter is equal to or greater than 13. In someembodiments, the Q parameter is equal to or greater than 14. In someembodiments, the Q parameter is equal to or greater than 15.

Clause 29: the method of clause 27 or clause 28, further comprisingheating the material to a temperature between about 50° C. and about125° C.

Clause 30: the method of any one of clauses 27 to 29, further comprisinga bleaching step.

Clause 31: the method of any one of clauses 27 to 30, wherein IN islinked to, or part of, the matrix, as in Formula II:

Clause 32: the method of any one of clauses 27 to 31, wherein INcomprises an alkyl amine or a carboxyl group.

Clause 33: the method of any one of clauses 27 to 32, wherein x is 0, asin Formula III:

and wherein

is an optional link to the matrix.

Clause 34: the method of any one of clauses 27 to 33, wherein the groupof Formula I, Formula II, or Formula III is selected from the groups ofFormulas 101 to 107, wherein

is an optional link to the matrix:

Clause 35: the method of any one of clauses 27 to 34, wherein M isselected from an optionally substituted acrylate, an optionallysubstituted methacrylate, an optionally substituted acrylamide, anoptionally substituted methacrylamide, an optionally substitutedstyrene, an optionally substituted vinyl derivative, and an optionallysubstituted allyl derivative.

Clause 36. The method of any one of clauses 27, 28, 29, 30, 31, 32, or34, wherein x is at least 1, and -[M]- is selected from a polymerizedoptionally substituted acrylate, a polymerized optionally substitutedmethacrylate, a polymerized optionally substituted acrylamide, apolymerized optionally substituted methacrylamide, a polymerizedoptionally substituted styrene, a polymerized optionally substitutedvinyl derivative, and a polymerized optionally substituted allylderivative.

Clause 37: the method of any one of clauses 27, 28, 29, 30, 31, 32, 34,or 35, wherein any one of Formulas I, II, and 101 to 106 is selectedfrom the groups of Formulas 1001 to 1011:

wherein: x is at least 1; R¹ is selected from hydrogen, optionallysubstituted alkyl, optionally substituted heteroalkyl, optionallysubstituted alkenyl, optionally substituted alkynyl, optionallysubstituted cycloalkyl, optionally substituted heterocycloalkyl,optionally substituted aryl, optionally substituted arylalkyl,optionally substituted heteroaryl, and optionally substitutedheteroarylalkyl; R² is independently a group of one, two, three, or fourindependently selected substituents, or no substituent, each substituentindependently comprising one or more groups selected from optionallysubstituted alkyl, optionally substituted heteroalkyl, optionallysubstituted alkenyl, optionally substituted alkynyl, optionallysubstituted cycloalkyl, optionally substituted heterocycloalkyl,optionally substituted aryl, optionally substituted arylalkyl,optionally substituted heteroaryl, optionally substitutedheteroarylalkyl, hydroxy, halo, cyano, trifluoromethyl,trifluoromethoxy, nitro, trimethylsilanyl, —OR^(a), —SR^(a),—OC(O)—R^(a), —N(R^(a))₂, —C(O)R^(a), —C(O)OR^(a), —OC(O)OR^(a),—OC(O)N(R^(a))₂, —C(O)N(R^(a))₂, —N(R^(a))C(O)OR^(a),—N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂, N(R^(a))C(NR^(a))N(R^(a))₂,—N(R^(a))S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)OR^(a),—S(O)_(t)N(R^(a))₂, —S(O)_(t)N(R^(a))C(O)R^(a), (O)P(OR^(a))₃,(S)P(OR^(a))₃, and —(O)P(OR^(a))₂; R³ is selected from optionallysubstituted alkyl, optionally substituted heteroalkyl, optionallysubstituted alkenyl, optionally substituted alkynyl, optionallysubstituted cycloalkyl, optionally substituted heterocycloalkyl,optionally substituted aryl, optionally substituted arylalkyl,optionally substituted heteroaryl, optionally substitutedheteroarylalkyl, trifluoromethyl, trifluoromethoxy, nitro,trimethylsilanyl, —OR^(a), —SR^(a), —OC(O)—R^(a), —N(R^(a))₂,—C(O)R^(a), —C(O)OR^(a), —OC(O)OR^(a), —OC(O)N(R^(a))₂, —C(O)N(R^(a))₂,—N(R^(a))C(O)OR^(a), —N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂,N(R^(a))C(NR^(a))N(R^(a))₂, —N(R^(a))S(O)_(t)R^(a), —S(O)_(t)OR^(a),—S(O)_(t)N(R^(a))₂, —S(O)_(t)N(R^(a))C(O)R^(a), —O(O)P(OR^(a))₂, and—O(S)P(OR^(a))₂; t is 1 or 2; and R^(a) is independently selected fromhydrogen, optionally substituted alkyl, optionally substitutedheteroalkyl, optionally substituted alkenyl, optionally substitutedalkynyl, optionally substituted cycloalkyl, optionally substitutedheterocycloalkyl, optionally substituted aryl, optionally substitutedarylalkyl, optionally substituted heteroaryl, and optionally substitutedheteroarylalkyl.

Clause 38: the method of any one of clauses 27 to 37, wherein thepolymer matrix comprises a polyurethane fragment.

Clause 39: the method of any one of clauses 27 to 38, wherein thepolyurethane is derived from an isocyanate selected from butylenediisocyanate, hexamethylene diisocyanate (HDI), isophorone diisocyanate(IPDI), 1,8-diisocyanato-4-(isocyanatomethyl)octane,2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylenediisocyanate, isomeric bis(4,4′-isocyanatocyclohexyl)methane and anyisomer thereof, isocyanatomethyl-1,8-octane diisocyanate,1,4-cyclohexylene diisocyanate, isomeric cyclohexanedimethylenediisocyanates, 1,4-phenylene diisocyanate, 2,4-toluene diisocyanate,2,6-toluene diisocyanate, 1,5-naphthylene diisocyanate,2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate,and triphenylmethane 4,4′,4″-triisocyanate.

In some embodiments, the disclosure provides a volume Bragg gratingrecorded on any recording material described herein, where the gratingis characterized by a Q parameter equal to or greater than 5, where

$Q = \frac{2{\pi\lambda}_{0}d}{n_{0}\Lambda^{2}}$

where λ₀ is a recording wavelength, d is the thickness of the recordingmaterial, n₀ is a refractive index of the recording material, and Λ is agrating constant. In some embodiments of a polymeric material describedherein including any of Formulas I, II, 101 to 106, and 1001 to 1011,the group of any of Formulas I, II, 101 to 106, and 1001 to 1011, isanisotropically distributed throughout the material. In someembodiments, the portions of material having a high concentration of anyof Formulas I, II, 101 to 106, and 1001 to 1011, form a virtual Bragggrating, where the grating is characterized by a Q parameter equal to orgreater than 10, where

$Q = \frac{2{\pi\lambda}_{0}d}{n_{0}\Lambda^{2}}$

and where λ₀ is a recording wavelength, d is the thickness of therecording material, n₀ is a refractive index of the recording material,and Λ is a grating constant. In some embodiments, the disclosureprovides a volume Bragg grating obtained by heating any polymericmaterial described herein.

In some embodiments, a volume Bragg grating may be recorded on aholographic material layer by exposing the holographic material layer tolight patterns generated by the interference between two or morecoherent light beams. FIG. 5A illustrates an example of a volume Bragggrating (VBG) 500. Volume Bragg grating 500 shown in FIG. 5A may includea transmission holographic grating that has a thickness D. Therefractive index n of volume Bragg grating 500 may be modulated at anamplitude n₁, and the grating period of volume Bragg grating 500 may beΛ. Incident light 510 having a wavelength λ may be incident on volumeBragg grating 500 at an incident angle θ, and may be refracted intovolume Bragg grating 500 as incident light 520 that propagates at anangle θ_(n) in volume Bragg grating 500. Incident light 520 may bediffracted by volume Bragg grating 500 into diffraction light 530, whichmay propagate at a diffraction angle θ_(d) in volume Bragg grating 500and may be refracted out of volume Bragg grating 500 as diffractionlight 540.

FIG. 5B illustrates the Bragg condition for volume Bragg grating 500shown in FIG. 5A. Vector 505 represents the grating vector {right arrowover (G)}, where |{right arrow over (G)}|=2π/Λ. Vector 525 representsthe incident wave vector {right arrow over (k_(l))}, and vector 535represents the diffract wave vector {right arrow over (k_(d))}, where|{right arrow over (k_(l))}|=|{right arrow over (k_(d))}|=2πn/λ. Underthe Bragg phase-matching condition, {right arrow over (k_(l))}−{rightarrow over (k_(d))}={right arrow over (G)}. Thus, for a given wavelengthλ, there may only be one pair of incident angle θ (or θ_(n)) anddiffraction angle θ_(d) that meet the Bragg condition perfectly.Similarly, for a given incident angle θ, there may only be onewavelength λ that meets the Bragg condition perfectly. As such, thediffraction may only occur in a small wavelength range and a smallincident angle range. The diffraction efficiency, the wavelengthselectivity, and the angular selectivity of volume Bragg grating 500 maybe functions of thickness D of volume Bragg grating 500. For example,the full-width-half-magnitude (FWHM) wavelength range and the FWHM anglerange of volume Bragg grating 500 at the Bragg condition may beinversely proportional to thickness D of volume Bragg grating 500, whilethe maximum diffraction efficiency at the Bragg condition may be afunction sin² (a×n₁/D), where a is a coefficient. For a reflectionvolume Bragg grating, the maximum diffraction efficiency at the Braggcondition may be a function of tanh² (a×n₁×D).

In some embodiments, a multiplexed Bragg grating may be used to achievea desired optical performance, such as a high diffraction efficiency andlarge FOV for the full visible spectrum (e.g., from about 400 nm toabout 700 nm, or from about 440 nm to about 650 nm). Each part of themultiplexed Bragg grating may be used to diffract light from arespective FOV range and/or within a respective wavelength range. Thus,in some designs, multiple volume Bragg gratings each recorded under arespective recording condition may be used.

The holographic optical elements described herein may be recorded in aholographic material (e.g., photopolymer) layer. In some embodiments,the HOEs can be recorded first and then laminated on a substrate in anear-eye display system. In some embodiments, a holographic materiallayer may be coated or laminated on the substrate and the HOES may thenbe recorded in the holographic material layer.

In general, to record a holographic optical element in a photosensitivematerial layer, two coherent beams may interfere with each other atcertain angles to generate a unique interference pattern in thephotosensitive material layer, which may in turn generate a uniquerefractive index modulation pattern in the photosensitive materiallayer, where the refractive index modulation pattern may correspond tothe light intensity pattern of the interference pattern. Thephotosensitive material layer may include, for example, silver halideemulsion, dichromated gelatin, photopolymers includingphoto-polymerizable monomers suspended in a polymer matrix,photorefractive crystals, and the like. FIG. 6A illustrates therecording light beams for recording a volume Bragg grating 600 and thelight beam reconstructed from volume Bragg grating 600 according tocertain embodiments. In the example illustrated, volume Bragg grating600 may include a transmission volume hologram recorded using areference beam 620 and an object beam 610 at a first wavelength, such as660 nm. When a light beam 630 at a second wavelength (e.g., 940 nm) isincident on volume Bragg grating 600 at a 0° incident angle, theincident light beam 630 may be diffracted by volume Bragg grating 600 ata diffraction angle as shown by a diffracted beam 640.

FIG. 6B is an example of a holography momentum diagram 605 illustratingthe wave vectors of recording beams and reconstruction beams and thegrating vector of the recorded volume Bragg grating according to certainembodiments. FIG. 6B shows the Bragg matching conditions during theholographic grating recording and reconstruction. The length of wavevectors 650 and 660 of the recording beams (e.g., object beam 610 andreference beam 620) may be determined based on the recording lightwavelength λ_(c) (e.g., 660 nm) according to 2πn/λ_(c), where n is theaverage refractive index of holographic material layer. The directionsof wave vectors 650 and 660 of the recording beams may be determinedbased on the desired grating vector K (670) such that wave vectors 650and 660 and grating vector K (670) can form an isosceles triangle asshown in FIG. 6B. Grating vector K may have an amplitude 2π/Λ, where Λis the grating period. Grating vector K may in turn be determined basedon the desired reconstruction condition. For example, based on thedesired reconstruction wavelength λ_(r) (e.g., 940 nm) and thedirections of the incident light beam (e.g., light beam 630 at 0°) andthe diffracted light beam (e.g., diffracted beam 640), grating vector K(670) of volume Bragg grating 600 may be determined based on the Braggcondition, where wave vector 680 of the incident light beam (e.g., lightbeam 630) and wave vector 690 of the diffracted light beam (e.g.,diffracted beam 640) may have an amplitude 2πn/λ_(r), and may form anisosceles triangle with grating vector K (670) as shown in FIG. 6B.

As described herein, for a given wavelength, there may only be one pairof incident angle and diffraction angle that meets the Bragg conditionperfectly. Similarly, for a given incident angle, there may only be onewavelength that meets the Bragg condition perfectly. When the incidentangle of the reconstruction light beam is different from the incidentangle that meets the Bragg condition of the volume Bragg grating or whenthe wavelength of the reconstruction light beam is different from thewavelength that meets the Bragg condition of the volume Bragg grating,the diffraction efficiency may be reduced as a function of the Braggmismatch factor caused by the angular or wavelength detuning from theBragg condition. As such, the diffraction may only occur in a smallwavelength range and a small incident angle range.

FIG. 7 illustrates an example of a holographic recording system 700 forrecording holographic optical elements according to certain embodiments.Holographic recording system 700 includes a beam splitter 710 (e.g., abeam splitter cube), which may split an incident laser beam 702 into twolight beams 712 and 714 that are coherent and may have similarintensities. Light beam 712 may be reflected by a first mirror 720towards a plate 730 as shown by the reflected light beam 722. On anotherpath, light beam 714 may be reflected by a second mirror 740. Thereflected light beam 742 may be directed towards plate 730, and mayinterfere with light beam 722 at plate 730 to generate an interferencepattern. A holographic recording material layer 750 may be formed onplate 730 or on a substrate mounted on plate 730. The interferencepattern may cause the holographic optical element to be recorded inholographic recording material layer 750 as described above. In someembodiments, plate 730 may also be a mirror.

In some embodiments, a mask 760 may be used to record different HOEs atdifferent regions of holographic recording material layer 750. Forexample, mask 760 may include an aperture 762 for the holographicrecording and may be moved to place aperture 762 at different regions onholographic recording material layer 750 to record different HOEs at thedifferent regions using different recording conditions (e.g., recordingbeams with different angles).

Holographic materials can be selected for specific applications based onsome parameters of the holographic materials, such as the spatialfrequency response, dynamic range, photosensitivity, physicaldimensions, mechanical properties, wavelength sensitivity, anddevelopment or bleaching method for the holographic material.

The dynamic range indicates how much refractive index change can beachieved in a holographic material. The dynamic range may affect, forexample, the thickness of the device for high efficiency and the numberof holograms that can be multiplexed in the holographic material. Thedynamic range may be represented by the refractive index modulation(RIM), which may be one half of the total change in refractive index.Small values of refractive index modulation may be given as parts permillion (ppm). In generally, a large refractive index modulation in theholographic optical elements is desired in order to improve thediffraction efficiency and record multiple holographic optical elementsin a same holographic material layer.

The frequency response is a measure of the feature size that theholographic material can record and may dictate the types of Braggconditions that can be achieved. The frequency response can becharacterized by a modulation transfer function, which may be a curvedepicting the sinusoidal waves of varying frequencies. In general, asingle frequency value may be used to represent the frequency response,which may indicate the frequency value at which the refractive indexmodulation begins to drop or at which the refractive index modulation isreduced by 3 dB. The frequency response may also be represented bylines/mm, line pairs/mm, or the period of the sinusoid.

The photosensitivity of the holographic material may indicate thephoto-dosage required to achieve a certain efficiency, such as 100% or1% (e.g., for photo-refractive crystals). The physical dimensions thatcan be achieved in a particular holographic material affect the aperturesize as well as the spectral selectivity of the HOE device. Physicalparameters of holographic materials may be related to damage thresholdsand environmental stability. The wavelength sensitivity may be used toselect the light source for the recording setup and may also affect theminimum achievable period. Some materials may be sensitive to light in awide wavelength range. Development considerations may include how theholographic material is processed after recording. Many holographicmaterials may need post-exposure development or bleaching.

Embodiments of the invention may be used to fabricate components of anartificial reality system or may be implemented in conjunction with anartificial reality system. Artificial reality is a form of reality thathas been adjusted in some manner before presentation to a user, whichmay include, for example, a virtual reality (VR), an augmented reality(AR), a mixed reality (MR), a hybrid reality, or some combination and/orderivatives thereof. Artificial reality content may include completelygenerated content or generated content combined with captured (e.g.,real-world) content. The artificial reality content may include video,audio, haptic feedback, or some combination thereof, and any of whichmay be presented in a single channel or in multiple channels (such asstereo video that produces a three-dimensional effect to the viewer).Additionally, in some embodiments, artificial reality may also beassociated with applications, products, accessories, services, or somecombination thereof, that are used to, for example, create content in anartificial reality and/or are otherwise used in (e.g., performactivities in) an artificial reality. The artificial reality system thatprovides the artificial reality content may be implemented on variousplatforms, including a head-mounted display (HMD) connected to a hostcomputer system, a standalone HMD, a mobile device or computing system,or any other hardware platform capable of providing artificial realitycontent to one or more viewers.

FIG. 4 illustrates an example of an optical see-through augmentedreality system 400 using a waveguide display according to certainembodiments. Augmented reality system 400 may include a projector 410and a combiner 415. Projector 410 may include a light source or imagesource 412 and projector optics 414. In some embodiments, image source412 may include a plurality of pixels that displays virtual objects,such as an LCD display panel or an LED display panel. In someembodiments, image source 412 may include a light source that generatescoherent or partially coherent light. For example, image source 412 mayinclude a laser diode, a vertical cavity surface emitting laser, and/ora light emitting diode. In some embodiments, image source 412 mayinclude a plurality of light sources each emitting a monochromatic imagelight corresponding to a primary color (e.g., red, green, or blue). Insome embodiments, image source 412 may include an optical patterngenerator, such as a spatial light modulator. Projector optics 414 mayinclude one or more optical components that can condition the light fromimage source 412, such as expanding, collimating, scanning, orprojecting light from image source 412 to combiner 415. The one or moreoptical components may include, for example, one or more lenses, liquidlenses, mirrors, apertures, and/or gratings. In some embodiments,projector optics 414 may include a liquid lens (e.g., a liquid crystallens) with a plurality of electrodes that allows scanning of the lightfrom image source 412.

Combiner 415 may include an input coupler 430 for coupling light fromprojector 410 into a substrate 420 of combiner 415. Combiner 415 maytransmit at least 50% of light in a first wavelength range and reflectat least 25% of light in a second wavelength range. For example, thefirst wavelength range may be visible light from about 400 nm to about650 nm, and the second wavelength range may be in the infrared band, forexample, from about 800 nm to about 1000 nm. Input coupler 430 mayinclude a volume holographic grating, a diffractive optical elements(DOE) (e.g., a surface-relief grating), a slanted surface of substrate420, or a refractive coupler (e.g., a wedge or a prism). Input coupler430 may have a coupling efficiency of greater than 30%, 50%, 75%, 90%,or higher for visible light. Light coupled into substrate 420 maypropagate within substrate 420 through, for example, total internalreflection (TIR). Substrate 420 may be in the form of a lens of a pairof eyeglasses. Substrate 420 may have a flat or a curved surface, andmay include one or more types of dielectric materials, such as glass,quartz, plastic, polymer, poly(methyl methacrylate) (PMMA), crystal, orceramic. A thickness of the substrate may range from, for example, lessthan about 1 mm to about 10 mm or more. Substrate 420 may be transparentto visible light.

Substrate 420 may include or may be coupled to a plurality of outputcouplers 440 configured to extract at least a portion of the lightguided by and propagating within substrate 420 from substrate 420, anddirect extracted light 460 to an eye 490 of the user of augmentedreality system 400. As input coupler 430, output couplers 440 mayinclude grating couplers (e.g., volume holographic gratings orsurface-relief gratings), other DOEs, prisms, etc. Output couplers 440may have different coupling (e.g., diffraction) efficiencies atdifferent locations. Substrate 420 may also allow light 450 fromenvironment in front of combiner 415 to pass through with little or noloss. Output couplers 440 may also allow light 450 to pass through withlittle loss. For example, in some implementations, output couplers 440may have a low diffraction efficiency for light 450 such that light 450may be refracted or otherwise pass through output couplers 440 withlittle loss, and thus may have a higher intensity than extracted light460. In some implementations, output couplers 440 may have a highdiffraction efficiency for light 450 and may diffract light 450 tocertain desired directions (i.e., diffraction angles) with little loss.As a result, the user may be able to view combined images of theenvironment in front of combiner 415 and virtual objects projected byprojector 410.

While preferred embodiments are shown and described herein, suchembodiments are provided by way of example only and are not intended tootherwise limit the scope of the disclosure. Various alternatives to thedescribed embodiments may be employed in practicing the disclosure.

A number of patent and non-patent publications are cited herein in orderto describe the state of the art to which this disclosure pertains. Theentire disclosure of each of these publications is incorporated byreference herein.

While certain embodiments are described and/or exemplified herein,various other embodiments will be apparent to those skilled in the artfrom the disclosure. The present disclosure is, therefore, not limitedto the particular embodiments described and/or exemplified, but iscapable of considerable variation and modification without departurefrom the scope and spirit of the appended claims.

The invention claimed is:
 1. A polymeric material comprising a resinmixture comprising: a partially or completely polymerized or crosslinkedpolymer matrix; a polymer precursor comprising a monomer M; and a groupof Formula I:

wherein IN is an initiating moiety optionally linked to, or part of, thematrix, -[M]- is a polymerized monomer, x is an integer from 0 to 50,and the group of Formula I is anisotropically distributed throughout thepolymeric material.
 2. The polymeric material of claim 1, wherein IN islinked to, or part of, the matrix, as in Formula II:


3. The polymeric material of claim 1, wherein IN comprises an alkylamine or a carboxyl group.
 4. The polymeric material of claim 1, whereinx is 0, as in Formula III:

and wherein

is an optional link to the matrix.
 5. The polymeric material of claim 2,wherein the group of Formula II is selected from the groups of Formulas101 to 106, wherein

is an optional link to the matrix:


6. The polymeric material of claim 1, wherein M is selected from anoptionally substituted acrylate, an optionally substituted methacrylate,an optionally substituted acrylamide, an optionally substitutedmethacrylamide, an optionally substituted styrene, an optionallysubstituted vinyl derivative, and an optionally substituted allylderivative.
 7. The polymeric material of claim 1, wherein x is at least1, and -[M]- is selected from a polymerized optionally substitutedacrylate, a polymerized optionally substituted methacrylate, apolymerized optionally substituted acrylamide, a polymerized optionallysubstituted methacrylamide, a polymerized optionally substitutedstyrene, a polymerized optionally substituted vinyl derivative, and apolymerized optionally substituted allyl derivative.
 8. The polymericmaterial of claim 2, wherein Formula II is selected from the groups ofFormulas 1001 to 1011:

wherein: x is at least 1; R¹ is selected from hydrogen, optionallysubstituted alkyl, optionally substituted heteroalkyl, optionallysubstituted alkenyl, optionally substituted alkynyl, optionallysubstituted cycloalkyl, optionally substituted heterocycloalkyl,optionally substituted aryl, optionally substituted arylalkyl,optionally substituted heteroaryl, and optionally substitutedheteroarylalkyl; R² is independently a group of one, two, three, or fourindependently selected substituents, or no substituent, each substituentindependently comprising one or more groups selected from optionallysubstituted alkyl, optionally substituted heteroalkyl, optionallysubstituted alkenyl, optionally substituted alkynyl, optionallysubstituted cycloalkyl, optionally substituted heterocycloalkyl,optionally substituted aryl, optionally substituted arylalkyl,optionally substituted heteroaryl, optionally substitutedheteroarylalkyl, hydroxy, halo, cyano, trifluoromethyl,trifluoromethoxy, nitro, trimethylsilanyl, —OR^(a), —SR^(a),—OC(O)—R^(a), —N(R^(a))₂, —C(O)R^(a), —C(O)OR^(a), —OC(O)OR^(a),—OC(O)N(R^(a))₂, —C(O)N(R^(a))₂, —N(R^(a))C(O)OR^(a),—N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂, N(R^(a))C(NR^(a))N(R^(a))₂,—N(R^(a))S(O)_(t)R^(a) (where t is 1 or 2), —S(O)_(t)OR^(a),—S(O)_(t)N(R^(a))₂, —S(O)_(t)N(R^(a))C(O)R^(a), (O)P(OR^(a))₃,(S)P(OR^(a))₃, and —(O)P(OR^(a))₂; R³ is selected from optionallysubstituted alkyl, optionally substituted heteroalkyl, optionallysubstituted alkenyl, optionally substituted alkynyl, optionallysubstituted cycloalkyl, optionally substituted heterocycloalkyl,optionally substituted aryl, optionally substituted arylalkyl,optionally substituted heteroaryl, optionally substitutedheteroarylalkyl, trifluoromethyl, trifluoromethoxy, nitro,trimethylsilanyl, —OR^(a), —SR^(a), —OC(O)—R^(a), —N(R^(a))₂,—C(O)R^(a), —C(O)OR^(a), —OC(O)OR^(a), —OC(O)N(R^(a))₂, —C(O)N(R^(a))₂,—N(R^(a))C(O)OR^(a), —N(R^(a))C(O)R^(a), —N(R^(a))C(O)N(R^(a))₂,N(R^(a))C(NR^(a))N(R^(a))₂, —N(R^(a))S(O)_(t)R^(a), —S(O)_(t)OR^(a),—S(O)_(t)N(R^(a))₂, —S(O)_(t)N(R^(a))C(O)R^(a), —O(O)P(OR^(a))₂, and—O(S)P(OR^(a))₂; t is 1 or 2; and R^(a) is independently selected fromhydrogen, optionally substituted alkyl, optionally substitutedheteroalkyl, optionally substituted alkenyl, optionally substitutedalkynyl, optionally substituted cycloalkyl, optionally substitutedheterocycloalkyl, optionally substituted aryl, optionally substitutedarylalkyl, optionally substituted heteroaryl, and optionally substitutedheteroarylalkyl.
 9. The polymeric material of claim 1, wherein thepolymer matrix comprises a polyurethane fragment.
 10. The polymericmaterial of claim 1, wherein portions of material having a higherconcentration of Formula I form a virtual Bragg grating, wherein thegrating is characterized by a Q parameter equal to or greater than 5,wherein $Q = \frac{2{\pi\lambda}_{0}d}{n_{0}\Lambda^{2}}$ and wherein λ₀is a recording wavelength, d is the thickness of the recording material,n₀ is a refractive index of the recording material, and Λ is a gratingconstant.